US researchers have found traces of an ancient lake on Mars recently, increasing hopes of discovering evidence that billions of years ago the Red planet hosted life.

  The lake, which dates back some 3.4 billion years, appears to have covered as much as 80 square miles and was up to 1,500 feet deep, said the team from the University of Colorado.

  “This is the first clear evidence of shorelines on the surface of Mars,” said Boulder’s research associate, Gaetano Di Achille, in a study published in the latest edition of Geophysical Research Letters.

  “The identification of the shorelines and accompanying geological evidence allows us to calculate the size and volume of the lake, which appears to have formed about 3.4 billion years ago.”

  Analysis of the images has shown the water carved out the canyon (溪谷) in which it was found, which then opened out into a valley depositing (使淤積) sediment (沉積) which formed a delta(三角洲).

  “Finding shorelines is a great discovery to us,” said assistant professor Brian Hynek, adding it showed the lake existed at a time when Mars was thought to have been cold and dry.

  Scientists believe the oldest surfaces on Mars formed during the wet and warm era known as the Noachan epoch, about 4.1 billion to 3.7 billion years ago.

  The newly discovered lake is believed to date from the Hesperian era and postdates the end of the warm and wet period on Mars by 300 million years, according to the study.

  Scientists believe deltas next to the lake may well hold secrets about past life on Mars as such places on Earth have become the natural deposits of organic carbon and other markers of life.

68. The size of the lake found on mars is_____.

  A. 80 square miles           B. 1,500 square miles 

C. 3.4 billion square miles D. 300 million square miles

69. When the lake existed, the weather on Mars was_____.

A. hot and wet  B. wet and warm  C. cold and dry  D. cold and wet

70. Why do scientists think deltas near the lake may hold secrets about past life on Mars?

A. Because similar places on Earth have become natural deposits of markers of life.

B. Because someone has put secrets about past life on Mars there.

C. Because past life has been found in other deltas on Mars.

D. Because some people are said to have already seen life marks there.

71. Which of the following statements is Not true according to the passage?

A. The Noachan epoch was a wet and warm era.

B. The lake might have existed 3.4 billion years.

C. The discovery can’t fully prove that the Mars once hosted life.

D. The lake traces prove that there exists life on Mars now.

練習冊系列答案
相關(guān)習題

科目:高中英語 來源:英語教研室 題型:054

   I grew up knowing I was different, and I   1   it. I was born with a misshapen lip. When my schoolmates asked, “What happened to your 2  ?” I’d tell them I’d fallen and   3   it on a piece of glass. Somehow it seemed   4   acceptable to have suffered an accident than to have been born   5  . I was sure that no one  6   my family could love me, or even liked me. Then I entered Mrs Leonard’s second-grade class.

   Mrs Leonard was round and pretty, with shining brown hair and warm, dark,   7   eyes. Everyone adored (敬重) her. But   8   came to love her more than I did. And for a   9   reason.

   The time came for the   10   tests given at our school. I could only just hear out of one ear, and was not   11  to reveal something else that would single   12   out as different. So I cheated.

   The “whisper test”   13   each child to go to the classroom door, turn sideways, close one ear with a finger,   14   the teacher whispered something from her desk,   15   the child repeated. Then the same for the other ear. Nobody checked how tightly the   16   ear was covered, so I only pretended to block mine.

   As  17   I was the last. But all through the testing I   18   what Mrs Leonard might say to me. I knew from previous years that the teacher   19   things like “The sky is blue.” Or “Do you have new shoes?”

   My   20   came. I turned my bad ear toward her,   21   the other just enough to be able to hear. I waited and then came the words that God had surely put into her mouth,   22   words that changed my life   23   .

   Mrs Leonard, the teacher I   24   , said softly, “I   25   you were my little girl.”

1   A. liked     B.    loved        C.   hated     D expected

2.    A. lip       B. ear          C.    finger       D. eyes

3.    A. broken       B.cut         C.   formed      D.killed

4.    A. very       B.much         C.   more      D.even

5.    A. strange     B.happy          C.    sad        D.different

6.    A. inside       B.with&nbtsp;         C.  as well as    D.outside

7.    A. surprised     B.smiling         C.frightening   D.blind

8.    A. everyone     B.no one        C. anyone      D.none  

9.    A. special     B.strange       C. usual      D.simple

10.   A. arithmetic算術(shù)  B.history       C.  hearing      D.     blood

11.   A. excitedly     B.when         C. about      D.how

12.   A. me        B.Mrs Leonard     C.     us         D.the pupils

13.   A. encouraged   B.persuaded        C.required       D.agreed

14.   A. if       B.so          C.as if       D.While

15.   A. that       B.what          C.     after       D.which

16.   A. untested     B.left          C.bad         D.tested

17.   A. usually      B.follows        C.usual        D.well

18.   A. examined    B.wondered        C.understood    D.noticed

19.   A. questioned   B.announced        C.shouted    D.whispered

20.   A. teacher      B.time         C.opportunity   D.chance

21.   A. picking up   B.plugging up         C.closing     D.opening

22.   A. seven     B.some           C.several      D.lovely

23.   A. sometimes   B.    usually         C.forever      D.all

24.   A. knew       B.adored           C.     realized      D.spoke

25.   A. expect      B.wish         C.wanted       D.knew

 

查看答案和解析>>

科目:高中英語 來源:設計必修一英語外研 題型:054

完形填空

  The house next door had been empty for so long that we had quite forgotten what it was to have neighbors.One day,   1  , a great furniture lorry drew up near our front gate and in a short time, all kinds of furniture were   2   on the pavement.A small car arrived, out of which came seven people, a man, a woman and five children of   3   ages.The children hurried out and began laughing   4   as the whole family moved into the house.Windows were   5   opens furniture was put into   6  ; and little faces looked curiously at us over the fence and disappeared.It was our first   7   to the Robinsons.

  Though we became firm   8   with our new neighbors, we often had causes to be made angry by them.Our garden became an unsafe place:little boys   9   as cowboys or Indians would jump up from behind bushes,   10   wooden guns at us and   11   us to put our hands up.Sometimes our lives were   12  ; at others, we were killed with a   13  “Bang!Bang!”.Even more dangerous were the arrows that occasionally came sailing   14   the garden fence.

  But we did not   15   go in fear for our lives.The Robinsons were friendly and helpful and when we left for the holidays, we knew we had nothing to fear   16   our neighbors were around.We understood what it was like to have   17   in the long, friendless, winter evenings   18  .Mr.Robinson would   19   in for a cup of tea and chat;or when Mr.Robinson would   20   over the fence and talk endlessly with father about gardening problems.

(1)

[  ]

A.

but

B.

therefore

C.

however

D.

strangely

(2)

[  ]

A.

unloaded

B.

removed

C.

loaded

D.

destroyed

(3)

[  ]

A.

the same

B.

various

C.

young

D.

middle

(4)

[  ]

A.

delightedly

B.

sadly

C.

astonishingly

D.

frighteningly

(5)

[  ]

A.

broken

B.

kicked

C.

forced

D.

pushed

(6)

[  ]

A.

place

B.

room

C.

order

D.

use

(7)

[  ]

A.

management

B.

introduction

C.

interview

D.

arrangement

(8)

[  ]

A.

enemies

B.

strangers

C.

friends

D.

relatives

(9)

[  ]

A.

looking

B.

pretending

C.

dressed

D.

worn

(10)

[  ]

A.

throw

B.

put

C.

fire

D.

point

(11)

[  ]

A.

ask

B.

order

C.

make

D.

lead

(12)

[  ]

A.

saved

B.

wasted

C.

devoted

D.

spared

(13)

[  ]

A.

soft

B.

sharp

C.

funny

D.

slow

(14)

[  ]

A.

on

B.

through

C.

over

D.

across

(15)

[  ]

A.

always

B.

ever

C.

sometimes

D.

then

(16)

[  ]

A.

unless

B.

though

C.

so long as

D.

even if

(17)

[  ]

A.

fun

B.

cheers

C.

discussions

D.

company

(18)

[  ]

A.

while

B.

when

C.

as

D.

since

(19)

[  ]

A.

drop

B.

slip

C.

jump

D.

break

(20)

[  ]

A.

climb

B.

fall

C.

lean

D.

lie

查看答案和解析>>

科目:高中英語 來源: 題型:閱讀理解

完形填空(共20小題;每小題1.5分,滿分30分)

  閱讀下面短文,掌握其大意,然后從36—55各題所給的四個選項(A,B,C和D)中,選出最佳選項。

  I went to Beijing this National holiday, and it was an interesting experience of my life.

  My friends told us that taking the “hard  36  ”to Beijing would be really terrible. So we didn’t know what to  37 . But we were pleasantly surprised when we finally boarded the

  38  , which was relatively modern and  39  . During the 14 - hour ride we ate peanuts and talked. It was not  40  at all.

  It was morning when we arrived. We stepped out of the railway station, having sat in hard seats and not getting much  41  . However, We had energy, First we tried to get teturn tickets to Shanghai, but the tickets seller  42  us that tickets would not be on  43  for another two days. We were a little worried about getting  44  , but we made up our minds to  45  for the hotel to put our bags down. After fighting our way  46  the“ gypsy”taxi drivers that tried to  47  us one hundred yuan for the ride, we found a taxi and it  48  cost us thirty yuan to get  49  we had planned to go. When we reached the hotel, there was a window for airplane and train tickets.  50  the man behind the counter could get tickets that day, which we

  51  . The most important lesson about China I ever  52  , is to get someone to do your work for you, and it seems to work out much  53  . We were not able to get tickets, but the

  54  agents(代理)could.

While in Beijing we saw a lot of places of interest, most of which were very  55  . It was fun to be with thousands of people in one place, There aren’t any words to describe it.

36.A. chair                       B. bed                         C. seat                         D. bench

37.A. provide                   B. expect                     C. happen                    D. think

38.A. plane                             B. bus                         C. ship                        D. train

39.A. quick                             B. clean                       C. simple                     D. long

40.A. bad                         B. good                       C. easy                        D. hard

41.A. trouble                    B. food                        C. sleep                       D. help

42.A. promised                 B. informed                 C. advised                    D. persuaded

43.A. time                        B. show                       C. duty                        D. sale

44.A. behind                    B. out                          C. through                   D. back

45.A. start                        B. ask                          C. look                        D. pay

46.A. towards                   B. into                         C. across                      D. past

47.A. offer                       B. charge                     C. bargain                    D. share

48.A. even                       B. still                         C. also                         D. only

49.A. what                       B. which                      C. where                      D. how

50.A. Somehow                B. However                 C. Therefore                D. Otherwise

51.A. wouldn't                  B. couldn't                   C. shouldn't                  D. needn't

52.A. learned                    B. taught                     C. offered                    D. heard

53.A. harder                     B. earlier                     C. later                        D. easier

54.A. business                  B. transport                  C. travel                             D. hotel

55.A. interesting                      B. crowded                  C. famous                    D. noisy

查看答案和解析>>

科目:高中英語 來源:2008年普通高等學校招生全國統(tǒng)一考試陜西卷英語試題 題型:閱讀理解


They say there are three ways to experience the Grand Canyon; on foot, on mules(騾子) or by air. We chose the first. Up early; my husband and I and our three children couldn’t wait to get started. We decided to walk along a lovely path named Bright Angel Trail.
As we set out, I was shocked at how narrow the path was. And I couldn’t help noticing that the other tourists weren’t like us. They had heavy backpacks, water bottles, and hats. But as usual we were dressed, As the sun rose higher, Arizona’s famous heat seemed to roast(烘烤) us. There was no shade and our legs were aching. We decided to go back, with the girl on my back and the boys far behind. By the time we finally got back, our legs were like jelly.
The next day, after we’d had a long rest and a good breakfast, we were ready for another view of the Canyon – by air. After our last walk, this would be the easiest thing in the world.
We called to each other excitedly as the plane took off and circled around the Canyon. But the smiles on our faces disappeared as the pilot tossed(翻轉(zhuǎn)) the plane around, pretending he was going to hit the ground. I shouted, “STOP, TAKE US BACK!” When we finally arrived back on land, once again our legs were like jelly. We hardly spoke as we drove back.
As I said, there are three ways to view the Grand Canyon. We never tried the mules, but personally I’d suggest a fourth: buy yourself a good magazine like National Geographic. That way, you can see the Canyon, without fear or tiredness.
【小題1】Which of the following is true according to the second paragraph?

A.They made a careful preparation before the trip
B.They children were more joyful than their parents.
C.Bright Angel Trail was not as lovely as they expected.
D.The summer heat prevented them from enjoying the view.
【小題2】The underlined expression “Our legs were like jelly” probably means            .
A.we were weakB.we were unhappy
C.we were dissatisfiedD.we were disappointed
【小題3】Which of the following best describes their Canyon trip by air?
A.It proved to be frightening.B.It was more comfortable
C.It turned out to be excitingD.It made each of them tired.
【小題4】We can infer from the passage that          .
A.experiencing the Canyon on mules would be the best way
B.one needs to dress less when visiting the Grand Canyon.
C.the writer was not serious when she made the suggestion.
D.the whole family narrowly escaped from the air accident.

查看答案和解析>>

科目:高中英語 來源:2010-2011學年四川省高三上學期入學考試英語卷 題型:完型填空

第二節(jié):完形填空(共20小題;每小題1分,滿分20分)

閱讀下面短文,掌握其大意,然后從每題所給的四個選項(A、B、C和D)中,選出最佳選項。

Mary had her own special kind of joy, and she knew exactly how to spread it around. She lifted children from  31  into laughter, love, and belonging. Each time she found a new  32  for a child, she gave the family one of her little homemade paper roses. It had become a  33  for her, and the families didn't ever forget it.

One evening, Mary was  34 a meeting for adoptive parents. One of the  35  fathers stood up to introduce himself. But before he spoke, he reached into his coat pocket and held up a  36 , red paper rose.

“Twenty years ago today, I felt alone and  37 . I didn't know the talents inside me or what was possible for me.

Then Mary  38  two wonderful people into my life. They taught me what it was like to feel  39 . They not only loved me  40 . They opened a world of  41  that I didn't know existed. My new parents told me, ‘Reach for your dreams!’

I did, and today I'm  42  to be giving that chance to a child who  43  just like me. My mother gave me this little rose. By now, all of you  44  where she got it so long ago.

Mary sent me a new rose just yesterday. And my new rose  45 a new spring, a beautiful new  46  for my own little girl. It  47  me to show her what unconditional love is, and to teach her to reach for her own beautiful dreams.

Thank you, Mary, for the special little things like roses that  48  our lives together. And thank you for all you've done for me and so many families over the years!”

One brief even can send our spirits soaring or  49  us in quiet to ponder a new beginning. 50  it is also the very small things, like Mary's roses, that tie together the meaningful things.

31.A. poverty                    B. loneliness              C. misery                   D. suffering

32.A. home               B. place             C. school             D. life

33.A. glory                B. favor              C. habit              D. tradition

34.A. organizing      B. planning                C. hosting             D. attending

35. A. new                 B. grateful                 C. kind               D. active

36. A. broken              B. faded                         C. treasured           D. dried

37.A. tasteless             B. powerless                C. priceless             D. worthless

38.A. directed             B. introduced             C. brought            D. accepted

39.A. loved            B. protected          C. cared             D. cheered

40.A. silently              B. continuously             C. unintentionally      D. unconditionally

41.A. necessities         B. possibilities                     C. beauties            D. riches

42.A. eager            B. willing                  C. proud             D. lucky

43.A. started out        B. came up                 C. turned out          D. grew up

44.A. understand         B. guess                     C. tell               D. know  

45.A. replaces           B. symbolizes               C. equals            D. creates

46.A. chance           B. mystery                    C. challenge           D. beginning

47.A. reminds              B. helps                        C. accompanies        D. drives

48.A. fix              B. close                C. tie                  D. gather

49.A. cause              B. push                        C. put                           D. leave

50.A. Yet               B. Besides                    C. Otherwise          D. Therefore

 

查看答案和解析>>

同步練習冊答案