The Greatest Mystery of Whales
　　The whale is a mammal—warm-blooded, air-breathing, giving birth to its young alive1, sucking them—and, like all mammals, originated on land. There are many signs of this. ___D_1____ from flippers, used for steering and stability, are traces of feet.
　　Immense strength is built into the great body of the big whales, and in fact most of a whale’s body is one gigantic muscle. The blue whale’s pulling __A__2____ has been estimated at 400 horsepower. One specimen was reported to have __C__3___ a whaling vessel for seven hours at the __B__4____ of eight knots.
　　An enraged whale will attack a ship. A famous __C__5____ of this was the fate of whaler Essex, which was sunk ___6__A_ South America early in the last century. More recently, steel ships have had their plates buckled2 in the same way. Sperm whales were known to __B___7____ the old-time whaleboats in their jaws and crush them.
　　The greatest mystery of whales is their diving ability. The sperm whale can ____8___C_ the bottom for his favourite food, the octopus. _A__9___ he is known to go as far down as 3,200 feet, where the pressure is 1,400 pounds, to the square inch. Doing ____10__A__ he will remain submerged as long as one hour. Two feats are involved in this: storing up enough _B___11____ (all whales are air-breathed) and withstanding the great change in pressure. Just __C__12___ he does it scientists have not determined. It is believed that some of the oxygen is stored in a special system of blood vessels, rather than just held3 in the lungs. And __A__13____ that a special kind of oil in his head is some sort of compensating mechanism that automatically adjusts the internal pressure of his body. But_C____14_____ you can’t bring a live whale4 into the laboratory for study, no one __B___15__ just how these things work.
　　1. A) Their B) His C) Theirs D) Its考试大论坛
　　2. A) strength B) width C) height D) length
　　3. A) eaten B) crashed C) towed D) lifted
　　4. A) distance B) rate C) voyage D) sail
　　5. A) picture B) film C) example D) book
　　6. A) off the coast of B) of the coast of C) away the coast of D) in the coast of
　　7. A) hit B) seize C) damage D) overturn
　　8. A) sink to B) rest on C) dive to D) hide on
　　9. A) In that search B) Because of this C) In spite of that D) In support of this
　　10. A) so B) such C) above D) the same来源:考试大网
　　11. A) air B) oxygen C) energy D) heat
　　12. A) what B) where C) how D) when
　　13. A) it is believed B) he believes C) we believe D) it believes
　　14. A) because of B) due to C) since D) owing to
　　15. A) communicates B) knows C) hears D) develops
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