18.Which animal has the fastest snapping jaw (突然合住的顎)?If you're guessing a shark or perhaps a larger animal,you'll have to think smaller.The trap-jaw ant,which lives in Central and South America,moves its mouth parts at 35to 63meters per second.Another way to think about this is that the ant's jaws close at 125to 233kilometers per hour.That's 2,300times faster than the blink of an eye.
Scientists were able to measure the amazing jaw speed using high-speed video techniques.Sheila Patek,a biologist,says the key is that the jaws have a springy (有彈性的) system,which is critical in getting explosive (爆發(fā)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 freed almost immediately when you let go of the arrow with your finger.That's exactly what really fast organisms are doing.
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 8.3centimeters into the air.That's like someone who is 1.7meters jumping 13meters 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.
33.The fast speed of the trap-jaw ants'jaws lies inB.
A.their light bodies
B.their springy systems
C.their living environment
D.the length of their jaws
34.What does the passage use"a bow and arrow"as an example to show?C
A.How an arrow gets so much energy to fly.
B.Why the trap-jaw ants have a springy system.
C.Why the trap-jaw ants'jaws move so fast.
D.How a bow and arrow works.
35.According to the passage,the trap-jaw ants'jaws keep them safe becauseD.
A.they can catch their enemies easily with their jaws
B.their jaws make them difficult to recognize
C.their jaws help them to find food easily
D.their jaws help them to escape from their enemies.
分析 本文是一篇科教類閱讀,文章主要介紹了一種有非凡能力的The trap-jaw ant--一種陷阱顎螞蟻.它們的顎有彈性系統(tǒng),從而使得它們能獲得爆發(fā)性的速度.靠這種技能使得它們的天敵很難抓住它們.
解答 BCD
33.B細(xì)節(jié)理解題.根據(jù)第二段the key is that the jaws have a springy (有彈性的) system,which is critical in getting explosive (爆發(fā)性的) speeds.可知關(guān)鍵是它們的顎有彈性系統(tǒng),從而獲得爆發(fā)性的速度.由此可知,說明有彈性的系統(tǒng)(springy systems)才是真正的原因.故選B.
34.C 推理判斷題.根據(jù)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.可知作者用弓和箭的例子來說明這種彈性系統(tǒng)的原理.故選C.
35.D 細(xì)節(jié)題.根據(jù)第四段often a group of ants will start jumping all at once.It would be hard for their enemies to grab just one.可知一群螞蟻經(jīng)常一起跳,這使得它們的天敵很難抓住它們.由此說明,這種方法能讓它們逃脫敵人的虎口.故選D.
點評 本文考察學(xué)生的理解推斷能力以及細(xì)心程度,只要抓住文章的關(guān)鍵詞,采用尋讀的方法查找細(xì)節(jié),就能找到正確答案.