题目内容：

A Cloud of Hope and Danger

A small cloud floats through the air in a hospital operating room. In the room a patient, suffering from cancer, lies on a table. The cloud surrounds(包围) the patient, covering her body and filling her lungs(肺). The cloud is not smoke or steam. It is made of millions of microscopic robots called nanorobots(纳米机器人). These tiny robots move from cell(细胞) to cell in the patient’s body, destroying the cancer.

Fighting cancer with nanorobots is only an idea today, but scientists say that it could be possible in the future. Using nanorobots for good purposes such as fighting disease or repairing the environment may be the solution to many of today’s problems.

However, nanorobots could be a dangerous risk as well. Since nanorobots are so tiny, they will have to work in large teams of many thousands to many millions. For this reason, nanorobots will have to be programmed to build themselves. Scientists will not have the ability to build millions of nanorobots one by one.

This ability to reproduce is making some scientists worried. What if something goes wrong in the programming? Quite a lot of crazy nanorobots would be far worse than any disease. Some people think that if they get out of control, nanorobots could destroy the Earth.

What should be done? Should we continue researching nanorobots or should we search for other methods? This is one of the many difficult decisions that we have to make in the future.

1.What is the cloud in the passage, smoke and steam or microscopic robots?

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2.What can be the good use of nanorobots for us?

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3.Why will nanarobots have to work in large teams?

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4.What makes it possible for nanorobots build themselves?

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5.Can you give the passage another title?

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6.Are you for or against using nanorobots in the future? Why?

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