题目内容
Most birds find it safe to sleep in the trees, but ________they have eggs or young chicks, they don’t use a nest.
A.why B.how C.unless D.where
C。
解析:
由they have eggs or young chicks与they don’t use a nest之间的逻辑关系可以推出该空表示“除非”，因此应填unless引导条件状语从句。
完形填空（共20小题；每小题1分，满分20分）
请认真阅读下面短文，从短文后各题所给的A、B、C、D四个选项中，选出最佳选项，并在答题卡上将该项涂黑。
Most people think of birds as feathered animals that fly. Scientists, 36 , do not define (给…下定义) birds as animals that fly, because some birds do not. Of the 10,000 or so species of birds, 46 cannot 37 . Flight plays a key role in 38 for most birds. It allows them to find food over a 39 area and to get away from enemies. Ancestors of flightless birds may have 40 their ability to fly because they had no regular predators (捕食者) or did not need to fly to find food. Rather than fly, some of these birds developed other 41 to catch food and avoid enemies. Two examples of 42 birds are penguins and ostriches.
43 birds that fly, penguins do not have wide wings or large feathers. In order to catch the fish they feed on, penguins use their powerful wings to swim 44 . And when they swim, they look as if they are flying through the water. The 45 of penguins’ bodies makes it possible for them to dive deep underwater, 46 their thick feathers protect them from the cold.
Ostriches are known for their long legs, long necks, and large size. To 47 themselves, they stay in groups and use their excellent sight and hearing to 48 enemies. As soon as 49 approaches, they can run at a speed of more than 65 kilometers per hour to 50 . In addition to using their strong legs to run, they can kick powerfully.
Not all flightless birds have been 51 in protecting themselves. Flightless birds on some islands had no enemies until people 52 . These birds were hunted and easily caught by people and the animals 53 by people. Human land development has 54 the habitats of some birds. A number of flightless birds 55 because they were unable to adapt to new conditions and new enemies.
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When many people see birds cleaning their feathers, they attribute it to vanity on the part of the bird. But, in reality, what they are doing is maintaining their wings, the instruments that they depend on for safe flight. If a bird’s wings are not in perfect condition, the bird either won’t be able to fly or won’t be able to control its flight. That is why after a long flight and even throughout the day, you will see them cleaning their feathers.
Most birds, if they get a chance, will take a bath at least once a day. They do this to get rid of the dust that has accumulated in their feathers throughout their flight s during the day. In dry or desert areas, birds will not always be able to find water in which to bath, but they still need to clean their feathers. What many birds will do is to take dust baths. They will roll around in dust until it covers their feathers. They will stand up, shaking the dust out, and then clean their feathers with their beaks (鸟嘴) as usual.
Baths are important for another reason. During the course of the day and night, many parasites (寄生虫) are attracted to birds. Bugs, mites, fleas and so on will try to reach birds and suck from their blood. Daily baths help to keep the parasites to a minimum.
Some birds, especially those that spend a lot of time in or around water, have skin glands (皮肤腺) that produce oil. After bathing, these birds will squeeze the glands to spread the oil over their wings to keep them free of water.
If you are a bird lover and have bird houses in your yard, it can be good to go to the extra step, providing a bird bath. Once the birds in your neighborhood discover it, you will be surprised at how popular it becomes as they periodically stop by to take their daily bath.
【小题1】What’s the passage mainly about?
| A．How birds clean themselves. | B．What birds enjoy doing. |
| C．Why baths matter so much to birds. | D．What bird lovers should do. |
| A．Most people think it good for birds to clean their feathers. |
| B．Most people show much interest in how birds clean themselves. |
| C．Most people believe that birds’ keeping themselves clean is necessary. |
| D．Most people think birds’ cleaning their feathers of no practical significance. |
| A．helps keep them healthy | B．keeps them free of any parasite |
| C．makes them more attractive | D．helps them relax enough |
| A．we should love birds as much as possible |
| B．birds enjoy cleaning themselves by bathing |
| C．we can be good bird lovers by bathing birds |
| D．birds like to come close to the people in a yard |