John loves reading,so he often gets lost in ____

问题描述:

John loves reading,so he often gets lost in ____
he is reading and doesn't take a break.
A.that B.what C.when D.while

B what在这里引导了一个宾语从句,what在从句中做的是reading的宾语
若用A that,应是lost inthe book that he is reading
CD显然都不对