问题补充：
The old scientist has made a great contribution the moon.
A. in explore
B. to explore
C. explore
D. to exploring
答案：
A. in explore
B. to explore
C. explore
(答案→)D. to exploring
解析：句意：这个老科学家已经对探索月球做出了很大的贡献。make a great contribution to (doing) sth. 意为“为某事做贡献”，to 在这里为介词，因此后面接名词、代词或动名词做宾语。
