一课一练B3阅读理解.docxVIP

Passage One Questions 21 to 25 are based on the following passage. The sea has always interested man. From it he can get food, minerals and treasure. For thousands of years, he could sail on it. But he could not go far beneath its surface. Man wants to explore deep into the sea. However, he is not a fish. Because he must breathe air, he cannot stay under the waters 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. He can wear a diving suit and have air pumped to him from above. He can carry a tank of air on his back and breathe through a hose and a mouthpiece. Water weighs 800 times as much as air. Tons of water pushes against a diver deep in the sea. His body is under great pressure. When a diver is under great pressure, his blood takes in some of the gases he breathes. As he rises to the surface, the water pressure becomes less. If the diver rises too quickly, the gases in his blood form bubbles. The diver is then suffering from the bends (潜水员病) . The bends can cause a diver to double up in pain. They can even kill him. 21. The passage is mainly concerned with ____________. A) problems in deep-sea exploration B) breathing difficulty under the water surface C) diving D) exploration of the sea 22. Which of the following is NOT true of the passage? A) Man can get a lot from the sea. B) Man can swim like fish. C) Man cannot stay under the water surface for long. D) The pressure in deep sea can be dangerous. 23. How can a diver breathe air? A) He can breathe specially mixed gases. B) He can breathe from a tank on his back. C) He can depend on the air pumped to him from above. D) All of the above. 24. When does a diver get the bends? A) When