who do you think ___ the letter into pieces?

问题描述:

who do you think ___ the letter into pieces?
A tore B tearing C torn D to tear
不明白为什么不是用主动B选择呢?

who tore the letter into pieces?是一个一般过去时的特殊疑问句,主语who主动发出了tore这个过去的动作了,do you think 只是一个独立的插入语部分,可以先不管它.