why are you so popular with your students?as a teacher,i seldom give my students so difficult a

题目

why are you so popular with your students?as a teacher,i seldom give my students so difficult a
problem ( )they cannot work out.
a:as b:that c:if d:in order that

答案

A
因为they cannot work out 这个从句中work out 这个短语动词（算出）缺宾语,所以只能用关系代词as,代 前文所指的“难题”,作work out 的宾语