根据短文理解，从A、B、C、D四个选项中选择正确答案填空。

    The world's population is larger and larger. There will 1 much more people next century. The earth will be more crowded and there must be a little room 2 each person. Perhaps there will be 3 room only on the earth a few centuries later. That will be serious to humans.

    So human are 4 of a good way to solve the problems.

    The moon is the 5 that is nearest to us. Maybe man will 6 on it some day. According to the scientists, studying, we know that there is no air, no plants, no water and no life there. So scientists are doing experiments 7 many ways. They 8 solve a lot of problems 9 humans can live on the moon. I'm sure the dream must 10 in the future. Maybe it is in the next century.