Question

Which animal has the fastest snapping jaw (颚)? If you're guessing a shark or perhaps a larger animal, you'll have to think smaller. The trap­jaw ant, which lives in Central and South America, moves its mouth parts at 35 to 63 meters per second. Another way to think about this is that the ant's jaws close at 125 to 233 kilometers per hour. That's 2, 300 times faster than the blink of an eye.

Scientists were able to measure the amazing jaw speed using high­speed video techniques. Sheila Patek, a biologist, says the key is that the jaws have a springy (有弹性的) system, which is critical in getting explosive (爆发性的) speeds.

Consider a bow and arrow. If you try to throw an arrow with your arm, it won't go very far. If you use a bow, elastic energy stored in the bow is released almost instantly when you release the arrow with your finger or a latch. The combination of the springy bow and latch mechanism is what makes the arrow zoom through the air.

Maybe even more amazing than how fast these ants grab food or even enemies is how they use this same energy to move. As the ant closes its jaws, it uses them to push off the ground—all faster than the eye can see without slow motion video. A snap of the jaw can send an ant up to 8.3 centimeters into the air. That's like someone who is 1.7 meters jumping 13 meters high! Not only can they quickly escape from enemies, but often a group of ants will start jumping all at once. It would be hard for their enemies to grab just one.

People have suspected the ants used their jaws to jump for over a century, but could only prove it with today's modern video equipment.

1.The fast speed of the trap­jaw ant's jaw lies in ________.

A．its light body

B．its springy system

C．its living environment

D．the length of its jaw

2.The passage uses “a bow and arrow” as an example to show ________.

A．how an arrow gets so much energy to fly

B．why the trap­jaw ants have springy system

C．why the trap­jaw ants jaws move so fast

D．how a bow and arrow works

3.Which of the following may amaze the scientists most?

A．How high the ants can leap by using their jaws.

B．How quickly the trap­jaw ants can move on the ground.

C．How wonderfully the springy system in the trap­jaw ants' jaws works.

D．How quickly the trap­jaw ants can grab food or enemies.

4.According to the passage, the trap­jaw ants' jaws keep them safe because ________.

A．they can catch their enemies easily with their jaws

B．their jaws make them difficult to recognize

C．their jaws help them find food easily

D．their jaws help them escape from their enemies

Answer

1.B

2.C

3.A

4.D

【解析】

试题分析：

1.B 细节题。根据第二段2,3行the key is that the jaws have a springy (有弹性的) system说明a springy (有弹性的) system才是真正的原因，故B正确。

2.C 推理题。在文章第三段Consider a bow and arrow. If you try to throw an arrow with your arm, it won't go very far. If you use a bow, elastic energy stored in the bow is released almost instantly when you release the arrow with your finger or a latch.作者用弓和箭的例子来说明这种弹性系统的原理，故C正确。

3.A 细节题。根据第四段1,2行Maybe even more amazing than how fast these ants grab food or even enemies is how they use this same energy to move.说明A正确。

4.D 细节题。根据第四段最后两行often a group of ants will start jumping all at once. It would be hard for their enemies to grab just one.说明这种方法能让它逃脱敌人的虎口。故D正确。

考点：考查科普类短文阅读