单选题 According to the passage lunar researchers have focused mostly on ______.

A、 the possibility of finding water on the Moon
B、 the lunar regolith
C、 cataloging various land formations
D、 craters and their origins

【正确答案】 D

【答案解析】细节理解题。由文章第二段最后一句话“Although various land forms were catalogued，the majority of astronomers attention was fixed on craters and their origins．”可知，“弹坑及其起源”是研究者主要关心的问题。