Question 1:C

Question 2:B

Question 3: D.

The article is a short article about underground cities, based on a science fiction novel.

Question 1: Details. According to the second line of the first paragraph, they found that the moon is full of underground cities. We can know that the reason is that the moon people live in underground cities.

Question 2: Details. According to the third paragraph of the article, B is correct.

Question 3: Main idea. The article is about underground cities, so D meets the requirements.