问题补充：
I have a big dream — I want to go into space, will take some time to realize, I guess.
A. which
B. it
C. what
D. where
答案：
(答案→)A. which
B. it
C. what
D. where
解析：句意：我有一个很大的梦想，一个我想要花一些时间才能实现的梦想—去太空。这句话用了非限制性定语从句，先行词是dream，定语从句中缺少主语，用关系代词which引导定语从句，选A。
