请问这到英语选择题为什么选D,麻烦详解下,
问题描述：
请问这到英语选择题为什么选D,麻烦详解下,
Nelson Mandela spent his time _____ in * thinking about to continue his fight for the black people's freedom.
A.locking
B.to lock
C.being locked
D.locked
为什么选D?
答
locked：用过去分词表示被关押的状态.没有被动语态.