根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。 选项中有两项为多余选项。
The sea has always interested man. From it he can get food, minerals, and treasure. 【小题1】 But he could not go far beneath its surface.
【小题2】 However, he is not a fish. He must breathe air, so he can’t stay under the water’s surface for any length of time. To explore deep water, man faces even more dangers and problems.
A diver who wants to stay under water for more than a few minutes must breathe air or a special mixture of gases. 【小题3】 He can carry a tank of air on his back and breathe through a nose and a mouthpiece. Water weighs 800 times as much as air. Tons of water pushes against a diver deep in the sea. 【小题4】
When a diver is under great pressure, his blood takes in some of the gases he breathes. As he rises to surface, the water pressure bees less. If the diver rises too quickly, the gases in his blood form bubbles(气泡). The diver is then suffering from the bends(潜水夫病). The bends can cause a diver to double up in pain. 【小题5】 A．His body is under great pressure. B．Scientists are trying to find more about the sea. C．For thousands of years, he could sail on it. D．They can even kill him.E. He can wear a diving suit and have air pumped to him from above.
F. The water pressure can cause a diver to breathe with difficulty.
G. Man wants to explore deep into the sea.C
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(答案→)C
解析：本文介绍了在几千年以前，人类就可以在海上航行，但是却无法潜入海下很远，人类很想探索深海，但人类不是鱼，潜入深海面临很多危险和困难。在深海中，大量的水挤在潜水员身上，他的身体承受巨大的压力，上岸后，可能会得潜水员病，潜水员病甚至会致命。
【小题1】考查句意理解和上下文串联：根据But he couldn’t go far beneath its surface. 可知这里想说在几千年以前，人类就可以在海上航行，但是却无法潜入海下很远，故选C。
【小题2】考查句意理解和上下文串联：根据However, he isn’t a fish. Because he must breathe air, he can’t stay under the water’s surface for any length of time. To explore deep water, man faces even more dangers and problems. 可知这里想说人类想要探索深海，故选G。
【小题3】考查句意理解和上下文串联：根据He can carry a tank of air on his back and breathe through a hose and a mouthpiece.可知这里想说他可以穿潜水服，从上面向下输送氧气，故选E。
【小题4】考查句意理解和上下文串联：根据Tons of water pushes against a diver deep in the sea.可知这里想说在深海中，大量的水挤在潜水员身上，他的身体承受巨大的压力，故选A。
【小题4】考查句意理解和上下文串联：根据The diver is then suffering from the bends（潜水员病）. The bends can cause a diver to double up in pain. 可知这里想说潜水员病甚至会致命，故选D