单选题 Why did a large population who once lived in a region of New Mexico suddenly leave there?
A. Because all the trees were cut down.
B. Because the weather forced them to leave.
C. Because the weather was determined by trees.
D. Because they wanted to live in a new place.

【正确答案】 A

【答案解析】事实细节题。题目问为什么曾经住在新墨西哥地区的许多人忽然离开了?从文章第四段第二句“the people had to leave because they had cut down all the trees”，可以知道原因，所以A项是正确答案。