单选题 According to some scientists, migratory (迁徙的) birds should be able to withstand (抵抗) the winter. A bird's feathery coat is a good protection against the cold. Because a bird is warm-blooded, its body temperature always remains unchanging, even if the temperature of its surroundings (周围环境) changes. The factors (因素) that bring about migratory behavior (行为) in birds are difficult to explain. It seems that this kind of behavior is not be learned but inborn. For example, many northern birds leave their summer homes while the weather is still warm and there is still enough food to eat. Bird migrations are probably regulated (调整) by the glandular system (腺性分泌系统). Scientists think that the changing length of the day is the factor that brings about migratory behavior. In an experiment, migratory birds were kept in artificially (人工地) lighted rooms. It was found that if periods of darkness were lengthened proportionately (按比例地), the glands of the birds became active. These glands {{U}}secrete{{/U}} hormones (荷尔蒙), which are chemicals that control lots of body functions (机能). Shorter periods of daylight seem to change the hormone balance of birds, so that they retain more fat. This stored fat is the fuel that provides the energy for a long flight. The same experiment showed that the birds became more excited as the artificial night was lengthened. It is probably no coincidence (巧合) that most birds begin their migratory flights during the night.

单选题Whatisthemanplanningtodo?

单选题Which is not mentioned in this article?

单选题C First-time dog owners may encounter (遇到) many problems getting to know and train their bets. Sometimes a puppy (小狗), or even an older dog, will chew their fingers or bite them. Even in play, this can really hurt. Unfortunately, many bet owners tolerate (容忍) this in a young dog. However when the dog gets larger, it is not fun to be bitten by it. Training a dog fever to place his teeth on human skin or clothing is an important lesson. From now on, if you feel your dog's teeth while you are playing with him, say "ouch" in a loud voice and move away from him. He will soon learn that when he bites, you will not play with him any more. Another bad habit that many people tolerate in their pets is allowing them to bite and held on to clothing. Don't let your dog do this to you. When he does something you want him to do, praise him and tell him he's a good dog. You can also give him a treat at the same time he performs the good behavior. Eventually he will learn which kind of behavior is acceptable and which is not. Remember that reward is more effective than punishment, if you reward your dog when he does what you want him to, he will become very well behaved. Also remember that puppies need to chew on something. So give him a sock with a knot tied in it or an old shoe. If he chews the wrong thing, take it away while saying "No" and give him something he can chew. If dogs are trained well, they will truly be your friends for a lifetime.

单选题Where does the conversation take place?

单选题Advertisement is mainly paid for by______.

单选题______three years since Nancy had her vacation.

单选题His position ______ him to make the decision by himself.

单选题Do you still remember ______ Jane at our son"s birthday party three months ago?

单选题Which of the following is best supported by the text?

单选题—Each of the students, working hard at his or her lessons, ______to go to university. —So do I.

单选题The most effective complaint can be made by ______.

单选题{{B}}B{{/B}} I came to India a year ago to find a village in which I could live and write, but it was many months before I settled down. I wasted a lot of time looking for the "typical" village. Yet no such thing exists. Often the villagers themselves were puzzled. Why had I come? I had put aside my work as a newspaper reporter because my ideas had changed. I had come to believe that what was happening in the developing countries was more important than anything else. But to understand how three-quarters of the world's people live, and how their future might affect ours, I felt that I first had to try and share their way of life. In the end I chose a mountain village because it was a little cooler than those in the plains. I took the bus from town along a rough road. Then came a rough walk down a path to the river. After this I began the climb into the hills. Every time I stopped to catch my breath, there was a wonderful sight After several hours walk the village was in sight.

单选题--He is ______ a brave man.--We can't admire his courage ______.

单选题{{B}}B{{/B}} The banana "tree" is actually not a real tree. This is because there is no wood in the stem(树干) rising above the ground. The stem is made up of leaves growing very close together, one inside the other. The leaves spread out at the top of the stem and rise in the air. Banana plants need a lot of care and attention. They must be provided with water if the normal rainfall doesn't supply enough. The area around the plants must be kept free of weeds and grass. About nine or ten months after planting, a flower appears on the banana plant. This flower is at the end of a long stalk(茎), which grows from the base up through the center of the stem and turns downward when it comes out from the top. Small bananas form on this flower stalk as it grows down- ward. Bananas really grow upside down. As the small bananas form on the stalk, they point down- ward, but as they grow they mm and point upward. Bananas are harvested while they are still green. Even when they are to be eaten where they are grown, they are not allowed to ripen on the plant. A banana that turns yellow on the plant loses its taste.

单选题WhathappenedtoWinstonChurchillin1954?A.Hewaseightyyearsold.B.Hebecamefamousforhisportrait.C.Hegavetheprimeministerapresent.

单选题— When will you come to see me, Dad? — I will go to see when you ______ the training course. A.will finish B.will have finished C.are finishing D.finish

单选题—I'm sorry, I was out when you were calling me. A. I didn't mind. B. It doesn't matter. C. Where have you been?

单选题Franz laughed at what his wife said because ______.