2. 外语
  3. Human sympathy【C1】______ whales is only natural of all the creatures in the sea.【C2】______ are closer relatives to us than thes

Human sympathy【C1】______ whales is only natural of all the creatures in the sea.【C2】______ are closer relatives to us than thes

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问题      Human sympathy【C1】______ whales is only natural of all the creatures in the sea.【C2】______  are closer relatives to us than these warm-blooded mammals. And how they got into the sea is one of the most fascinating stories of【C3】______ Most authorities believe that 60 million years ago ancestors of modern whales were four-legged, wolf-size animals living on the sea shores,【C4】______   an abundance of fish and shrimp tempted them to try wading.【C5】______ 10 to 15 million years, their bodies grew, forelegs shrank into flippers used for balance and steering and hind legs disappeared. As a result of some amazing transformations, they are now helpless on land. If stranded on a beach, they can barely breathe.
     With abundant【C6】______ of food, whales grew into the largest creatures that lived,【C7】______   larger than dinosaurs. A blue whale can grow to 100 feet. Its tongue is ten feet thick and heavier than an elephant. Some arteries are big enough for a child to swim【C8】______ . The half-ton heart has walls two feet thick and pumps eight tons of blood.【C9】______ its size comes awesome strength. A blue whale swimming【C10】______ 15 knots generates 1 000 horsepower.【C11】______   their size, these giants move at a good speed. An 18-ton whale can even【C12】______ 12 m. p. h., over short distances. A whale can【C13】______ to 9 000 pounds of food a day. The world’s biggest creature【C14】______ itself almost entirely on shrimp--like krill smaller than a person’s thumb.
     Maternal instincts are also【C15】______ . Because a calf is born underwater, the mother must get it to the surface before it【C16】______ Often another whale will help. The mother pushes it gently【C17】______ the baby is confident with its swimming--usually after about 30 minutes. If the calf is【C18】______ , she may support it on her back until it gradually rots away. Like all mammals, whale babies【C19】______ mother’s milk. And the milk is more than 30-percent fat, over 10-percent protein, and the babies grow extremely fast. A blue whale calf lengthens【C20】   two inches a day and gains an average seven pounds per hour.   
【C17】
选项 A、until
B、up to
C、while
D、unless
答案A
解析 连接词辨义 。根据句意“鲸鱼妈妈轻轻地推着小鲸鱼游动，直到小鲸鱼对自己的游泳技术很有信心为止”，所以应选择连词until“直到……才”。
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