题目内容
Bats are the only mammals(哺乳动物) which can fly properly. Other flying mammals have wings of thin skin which cover their sides between their front and back legs. They can only fly from tree to tree, but they cannot change direction when they want to.
All bats fly at night and most of them hunt for flying insects(昆虫), such as bees. The common bat finds its food by making a constant noise that the human ear cannot hear. The bat listens for echoes(回声) of the noise as it bounces(反射) off the insects showing the bat their position.
The Fruit bat feeds on many different kinds of fruit. It does not use echoes but instead has very large, special eyes to see even in low light. The largest Fruit bat has a wing length of 0.75 meters. The Vampire bat drinks the blood of large mammals, and a few bats catch fish, birds and even other bats.
1. Some flying mammals are not real flyers because _____.
A. they do not have wings B. their wings are too thin
C. they have skin between their legs D. they cannot turn around in the air
2. When common bats hunt for food they _____.
A. use echoes to kill the insects B. make a noise to draw insects to them
C. produce a sound and listen to the echoes D. listen noise made by the insects
3. Unlike other bats, the Fruit bat _____.
A. can see very well B. eats fruit and fish
C. has very long wings D. has excellent hearings
4.The word "it" in the second paragraph refers to _____.
A. the bat B. the echo C. the noise D. the insect
1.D2.C3.A4.C
【解析】略
At night, bats fly through the air, catching hundreds of insects and other small animals. But during the day, they hardly move at all. Instead, bats pass the time hanging upside down from a secret spot.
There are a couple of reasons why bats rest this way. First of all, it puts them in a position for takeoff. Unlike birds, bats can’t fly into the air from the ground. Their wings don’t produce enough lift to take off from a dead stop, and their hind legs are so small and underdeveloped that they can’t run to build up the necessary takeoff speed. Instead, they use their front claws to climb to a high spot, and then fall into flight.
During the hours when most enemies are active, bats gather where few animals would think to look and most can’t reach. This allows them to disappear from the world until night comes again. There’s also little competition for these resting spots, as other flying animals don’t have the ability to hang upside down.
Bats have a unique physiological adaptation that lets them hang around this way without using any energy. For you to hold your fist around an object tight, you contract(紧缩)several muscles in your arm, which are connected to your fingers by tendons(腱);as one muscle contracts, it pulls a tendon, which pulls one of your fingers closed. A bat’s talons(爪)close in the same way, except that their tendons are connected only to the upper body, not to a muscle. To hang upside down, a bat pulls its claws open with other muscles. To get the talons to take hold of the surface, the bat simply lets its body relax. The weight of the upper body pulls down on the tendons connected to the talons, causing them to hold tight. Therefore, the bat doesn’t have to do anything to hang upside down.
【小题1】Bats hang upside down because________.
A.they haven’t developed a pair of strong claws | B.they can’t start to fly from the ground directly |
C.they have no hind legs to support their body | D.they can’t find quiet places to stay during the day |
A.is to save their energy for night movement | B.is a way to fight against flying animals |
C.is a great way to hide from danger | D.is a skill to compete for the flying places |
A.Because their upper body is light. |
B.Because they have strong muscles. |
C.Because their talons are linked to muscles tightly. |
D.Because their tendons are linked to their upper body. |
A.The living habits of bats. | B.How and why bats hang upside down. |
C.The importance of bats’ hanging upside down. | D.How bats use their energy at night. |