6．
Everyone may know that animals do better in some things than our human beings．Scientists search the reasons．At last they think that one of the skills which many animals have is homing instinct（本能）．These animals such as pigeons，bees，salmons，frogs and cats are able to find their way home，sometimes making journeys of hundreds of kilometers back home．
In our daily life，humans can make use of an animal's homing instinct．Pigeons，for example have been used to carry messages or letters to the battles in times of war．Nowadays some people join in the Pigeon Association with the pigeons they have trained because they
look on pigeon racing as a hobby and they even bet money on which pigeon would win the race organized by the association．
There are many interesting stories of the homing instinct at work．In the USA a cat traveled 1，360kilometers back to its old home after the owners moved，taking nearly a year over the journey．When we lose our cat，we usually find her again near the house where she was born．We have a pond in the garden where the frogs come back every year．I even heard a dog which was injured by a car managed to take itself to a doctor who cares for animals!
There are other wonderful stories about the homing instinct～But how do these animals find their way home？They don't have satellite guidance with them，they can't read maps and，as far as we know，they can't ask each other for directions．It seems that some animals，such as salmons，use their sense of smell to take them back to the place where they were born．Other animals such as birds and bees may use the sun，the stars and the moon to help them find their way．There is a theory that some animals have magnetic（磁的） cells in their brain which help them to find their way．As far as cats are concerned，nobody really knows how their homing instinct works and I am sure cats are never going to give away their secrets．
Finally，a joke about the homing instinct：
Question：What will you get if you cross（雜交） a pigeon with a parrot？
Answer：A bird which can stop and ask the way home!
根據(jù)材料內(nèi)容選擇最佳答案，并將其標號填入題前括號內(nèi)．
51．C use their sense of smell to return hometown．
A．Birds
B．Bees
C．Salmons
D．Pigeons
52．Which of the following is TRUE according to the passage？B
A．Ancient people used to make money by holding pigeon races．
B．The writer has collected many stories about the animals．
C．All the animals can go back home from far away places．
D．The writer knows exactly how animals'homing instinct works．
53．What's the best title for the passage？C
A．Animals and their Living Habits．
B．A Good Way to Protect Animals．
C．A Special Skill of the Animals．
D．All Kinds of Animals in Nature．
54．What does the underlined phrase"give away"probably mean in the passage？A
A．泄露
B．觀察
C．炫耀
D．分發(fā)
55．What can we infer from the passage？D
A．We should learn from nature and make inventions．
B．We must stop the experiments on animals at once．
C．We have already known everything well in nature．
D．We still need to make clear some secrets of nature．
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