They are surprised at_____I have told them A.tha

题目

They are surprised at_____I have told them A.tha
They are surprised at_____I have told them A.that B .which C .all that 为什么不选B 而选C

答案

c
all that相当于what,是定语从句I have told them的间接宾语.which通常放在它所指代的名词之后,是名词之后,这一点很重要.原句显然不是,在它前面的是介词at.