You're not the same person you were as a child. You're not even the same personyou were five years ago. We don't just mean your personality. While we'd love tostart a never-ending discussion over the “true self”，we're here to talk about thecells（細(xì)胞）in your body.

Do you know how your fingernails and hair are constantly growing and replacingthemselves? The same thing happens almost everywhere in your body. Your outerlayer of skin makes way for fresher skin, and inside your veins（血管），blood cells turn over to make wayfor fresh blood. It's probably no surprise that these types of cells are short-lived, even some of the mostseemingly permanent（永久的）parts of your body replace themselves over time-including your bones.

Strong as your bones might seem, the cells they're made of won't last a lifetime. Bones are masters at rebuilding themselves, which is why most broken bones can heal on their own into the right shape.

Bones have special cells called osteoclasts（破骨細(xì)胞）whose job is to break down bone, even if itisn't broken, and send the minerals into the blood stream. This may sound frighteningly like your bonesare wearing away, but your body knows what it's doing. As osteoclasts break down bone, osteoblasts（成骨細(xì)胞）build up new bone to replace the old. By the end of each year, about 10 percent of yourentire adult skeleton will have been rebuilt through this process.

If 10 percent of your bone breaks down every year, it must take about ten years to renew 100percent of your skeleton. That would be a great guess, and it lines up nicely with the medical myth thatthe human body's cells are fully replaced every seven years, but the body is a bit more complex. That10 percent is just an average-some bone grows faster than that, and some grows slower. While someparts of your bone will turn over quickly, other parts will stick around for decades. In fact, most bonecells could live as long as 50 years.

So before you get wrapped up in an identity crisis（危機）about the cells in your body disappearingon you, know that you can lose some hair and you can cut your nails, but the bones of you aren't goinganywhere-at least not very soon and not all at once.

【1】Which of the following is TRUE according to the passage?

A. All the cells in our body are the same ones that we were born with.

B. Our blood cells are constantly growing and replacing themselves.

C. It must take about 10 years to rebuild 100 percent of our skeleton.

D. Osteoblasts can break down skin and also rebuild it over time.

【2】The underlined words "wearing away" probably mean“＿＿”．

A. building upB. taking offC. dying outD. turning on

【3】What does the passage mainly talk about?

A. Our skeleton seems permanent but renews itself over time.

B. It is not surprising that some cells in our body are short-lived.

C. There are two types of cells in our bones: osteoclasts and osteoblasts.

D. We are not the same person we were five years ago because of personality.

My name is Jackson. I'm a great reader with good memory. I rememberalmost everything I read. But I don't like to speak in class. When Mr.Knoll announced an oral book report, the idea of going up and having myclassmates staring at me while I talked filled me with anxiety.

As for the date, if the book report was due in two weeks, I would do itright then. Mr. Knoll, though, gave us a month to get the report ready, so Ithought I had plenty of time.

Finally, I chose Fire-Hunter by Jim Kjelgaard. It looked really interesting. I read the first few pagesand then I set it aside. I wasn't worried. I had plenty of time. Then the book got buried in the clutter(雜物）in my room.

Before I knew it, the date of the book report was a week away. Some kids had already finished. Iwas in a panic. I raced home and found the book. Trembling（顫抖），I turned to the back and discoveredthere were 218 pages! I read like crazy

The last day came. When Mr. Knoll called on me to give my report, I still had eighty pages to go.

The class looked sorry for me when I pulled myself forward. They could see my fear.

"My book is Fire-Hunter, by Jim Kjelgaard," I began slowly. Then I started to tell the story and theclass seemed interested. To my surprise, I discovered I was enjoying myself. However, I had no ideahow the book ended. I really didn't know what came over me. I made up the rest of the story on the spot.The class loved it, and applauded as I finished.

At break time, Mr. Knoll called me over. "You know, Jackson, I don't really remember the book

ending that way."

I gulped（倒吸氣）．

"You told a pretty good story，”he continued. "The assignment was an oral book report. You did a great job on the oral part’

"Uh, thanks," I said.

"When you actually finish Fire-Hunter, please come to me and give me the book report’

"Yes, I definitely will," I said. I knew I would never make that mistake again.

【1】How long did Mr. Knoll give students to prepare the book report?

A. One week.B. Two weeks.C. Three weeks.D. A month.

【2】We know from the passage that＿＿·

A. Jackson's classmates didn't like his story

B. Jackson was the first to finish his book report

C. Jackson had to give Mr. Knoll his book report later

D. Jackson was criticized for his bad oral book report

【3】Which of the following would be the best title for the passage?

A. Jackson's HobbyB. Jackson's Book Report

C. Jackson's ProblemD. Jackson's Good Memory

A. help B. helped C. helps

A. rains B. doesn’t rain C. will rain D. won’t rain

A. some; an B. some; a C. some; some D. any; any

A. good at B. look like

C. good with D. good for

It was the middle of July. I had spent two days exploring a bat cave in thedesert in southern New Mexico. The cave was part of an ancient flow of lava（熔巖流），now hardened into rock. I had left the cave and was driving my pickup truckon a rough（高低不平的）track across the________surface of the lava flow.

Suddenly, the truck came to a stop, caught on a black lava rock.

A quick check of the underside ______the worst: the truck's axle（車軸）was bent，nearly broken intwo. I couldn't ______ help in such faraway country. I put the food and cans of water into my backpackand set off on foot, going north, the direction of the main highway．I was low on water. Too little food didnot matter much, but hiking across the desert in July without water could be dangerous. As I set out,unreasonable ______ came over my mind. I was afraid of everything around me. Each creature mademy heart jump. In my mind, every movement was a scary animal about to strike and kill me.

I walked for hours and cried until I________that nobody was around to hear me. Complaining wasuseless. A change came over me. I began to feel less afraid. Fear was replaced by curiosity. I went on,and slowly but surely began to see the desert world differently, through_______ eyes, not frightened ones.That night I lay on the warm sand, using my backpack as a pillow. The sky went dark. The starsbegan to shine in the hugeness of the heavens. With a smile I thought how little there was to fear, afterall. By noon the following day I ______north. I began to think how lucky I was to see the wild desertworld. A wrecked truck and a forced hike across the desert gave me an/a ______ to see what few othersever saw

Late in the day, I came to a farmhouse. I drank all the lemonade that the farmer and his wife had intheir refrigerator. "I liked it out there," I told them when we got to talking. "I just wish I had been lessfrightened. I would have noticed more that way "I know what you mean," the man said thoughtfully."It's a rare sight, that desert wilderness, a rare sight’

【1】A. cleanB. flatC. hardD. smooth

【2】A. provedB. orderedC. thoughtD. imagined

【3】A. chooseB. explainC. suggestD. expect

【4】A. prideB. fearsC. painsD. surprise

【5】A. wonderedB. rememberedC. describedD. realized

【6】A. tiredB. nervousC. interestedD. satisfied

【7】A. continuedB. searchedC. improvedD. increased

【8】A. changeB. opportunityC. attentionD. responsibility

A. at B. under C. on

A、stick B、greet C、examine

A. good; good B. well; well

C. good; well D. well; good