A、The moon. B、Other planets. C、Both A and B. D、Neither A nor B. A细节题。见第二段第二句，“the moon is the nearest to the earth in space，and

Of all the stars the sun is the nearest to the earth. Millions of other stars are even bigger and brighter than the sun. They look small only because they are much father away. You can’t see them in the daytime. But if you go out at night，you’ll be able to see thousands of them.
    The earth is one of the sun’s planets，and the moon is the nearest to the earth in space，and men have visited it already. No man has traveled farther than the moon，but spaceships without people have reached other planets.
    Many countries have sent up man-made satellites to circle the earth. With their help，people have done much research in many fields of science. Our countries sometimes have sent up man-made satellites to send and receive TV programs. This has helped the people of China and other countries to understand each other better.