综合类A级：完形填空The Greatest Mystery
The whale is a mammal(哺乳动物)一warm—blooded，air-breathing，giving birth to its young alive，sucking them—and，like all mammals，originated on land，There are many signs of this．________(51)front flippers(鳍肢)，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________ (52)has been estimated at 400 horsepower．One specimen was reported to have________ (53) a whaling vessel for seven hours at the________ (54)of eight knots．
An enraged whale will attack a ship．A famous________ (55)of this was the fate of whaler Essex，which was sunk________(56)the coast of South America early in the last century．More recently ，steel ships have had their plates buckled(扭曲变形)in the same way．Sperm whales were known to________ (57)the old—time whaleboats in their jaw sand crush them．
The greatest mystery of whales is their diving ability．The sperm whale can
________ (58)the bottom for his favorite food，the octopus(章鱼)．________ (59)that search he is known to go as far down as 3，200 feet，where the pressure is 1，400 pounds，to the square inch．Doing________ (60)he will remain submerged(水下的)as long as one hour．Two feats(绝技)are involved in this：storing up enough________ (61)(all whales are air-breathed)and withstanding the great change in pressure．Just________(62)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 held in the lungs.And________ (63)is believed 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________ (64)you can’t bring a live whale into the laboratory for study，no one________(65)just how these things work.
51 A Their B Its C Theirs D Its
52 .A strength B width C height D length
53. A eaten B crashed C towed(拖) D lifted
54. A distance B rate C voyage D sail
55. A picture B film C example D book
56 .A 0ff B of C above D over
57. A hit B seize C damage D kick
58. A fly to B jump on C dive to D crawl on
59. A In B On C By D At
60 .A SO B such C above D the same
61. A water B oxygen C energy D heat
62 .A what B who C how D which
63 A it B he C she D there
64. A because of B due to C since D owing to
65 .A communicates B knows C hears D develops