I'm Molly Brown, a student from New York. Every day, there are {#blank#}1{#/blank#} terrible rules around me. In the morning, Mom's rules come—“Get up now and make your bed!”, “Don't leave your dirty dishes in the kitchen!” After that, I run to school {#blank#}2{#/blank#} I can't be late. At school, I also have more rules {#blank#}3{#/blank#} —don't be noisy, don't eat in class, …

    I can't play basketball after school except on weekends. Dad's rule is “You {#blank#}4{#/blank#} do your homework.” After dinner, I have to read a book. So I can't relax, {#blank#}5{#/blank#}. No games, no TV programs, only rules, rules.

    However, Dr. Know tells me that parents and school are sometimes {#blank#}6{#/blank#}, but they make rules to help us to behave well in daily life. I believe rules are necessary.

A Cloud of Hope and Danger

    In 2050, 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, {#blank#}1{#/blank#} her body and filling her lungs (肺). The cloud is not smoke or steam. It is made of millions of microscopic robots {#blank#}2{#/blank#} nano-robots (纳米机器人). These tiny robots move from cell (细胞) to cell in the patients' body, destroying the cancer cells.

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

    However, nano-robots could be a {#blank#}5{#/blank#} risk as well. Since nano-robots are so tiny, they will have to work in large teams of many thousands to 'many millions. {#blank#}6{#/blank#} this reason, nano robots will have to be programmed to build {#blank#}7{#/blank#}. Scientists will not have the ability to build millions of nano-robots one by one.

    This ability to reproduce (复制) is making some scientists worried. What if something goes wrong in the programming? Quite a lot of crazy nan-orobots would be far {#blank#}8{#/blank#} 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 {#blank#}9{#/blank#} nan-orobots or should we search for other methods? This is one of the many difficult {#blank#}10{#/blank#} that we have to make in the future.