excited Geoff Marcy most was whether there were planets in other solar system where life

问题补充：

excited Geoff Marcy most was whether there were planets in other solar system where life might exist.

A. It

B. That

C. What

D. Why

答案：

A. It

B. That

(答案→)C. What

D. Why

解析：句意：使Geoff Marcy高兴的是，是否在太阳系的其他的行星上有生命存在。这里缺少主语从句的连词，并且连词在从句中做主语，排除ABD，that在从句中不做成分，why不能做主语。故选C。