用方框中所给单词的适当形式填空，使短文完整、通顺．每词限用一次．

温馨提示：只要有大小写、单词拼写、语法等错误，均不给分．

bad   solute   cover   them   patient   danger   but   decide   able   research

A Cloud of Hope and Danger

A small cloud floats through the air in a hospital operating room （手术室）． In the room a patient， suffering from cancer， lies on a table． The cloud surrounds（包围） the patient， （1） 　　her body and filling her lungs（肺）． The cloud is not smoke or steam． It is made of millions of microscopic robots called nano﹣robots（纳米机器人）． These tiny robots move from cell（细胞） to cell in the（2） 　　body， destroying the cancer．

Fighting cancer with nano﹣robots is only an idea today，（3） 　　scientists say that it could be possible in the future． Using nano﹣robots for good purposes such as fighting disease or repairing the environment may be the（4） 　　to many of today's problems．

However， nano﹣robots could be a（5） 　　risk as well． Since nano﹣robots are so tiny， they will have to work in large teams of many thousands to many millions． For this reason， nano﹣robots will have to be programmed to build（6） 　　． Scientists will not have the ability to build millions of nano﹣robots one by one．

This（7） 　　to reproduce is making some scientists worried． What if something goes wrong in the programming？ Quite a lot of crazy nan﹣orobots would be far（8） 　　than any disease． Some people think that if they get out of control， nan﹣orobots could destroy the Earth．

What should be done？ Should we continue（9） 　　nan﹣orobots or should we search for other methods？ This is one of the many difficult（10） 　　that we have to make in the future．