Are you certain that this is （） in his letter？A.grandfather expressed

Are you certain that this is （） in his letter？A.grandfather expressed
B.what grandfather has expressed
C.grandfather has expressed
D.which grandfather has expressed答案：B难度：1知识点：词汇与结构部分\辅导书\书A\结构A
A.grandfather expressed
B.what grandfather has expressed
C.grandfather has expressed
D.which grandfather has expressed
正确答案：B
解析:词汇与结构部分\辅导书\书A\结构A