【题目】Stephen Hawking believes that the earth is unlikely to be the only planet ___________ life has developed gradually.
A. that B. which
C. whose D. where
在线课程【答案】D
【解析】考查定语从句。先行词是the only planet，定语从句缺少地点状语，用where引导定语从句。句意：Stephen Hawking认为地球不可能是生命逐渐发展的唯一星球。选B。