I wonder that makes him so sad.
A. why it does
B. what he does
C. how it is
D. what it is
网友回答
A. why it does
B. what he does
C. how it is
(答案→)D. what it is
解析：考查强调句型。强调句型的结构为：It is/was 被强调成分 that/who 其他成分。把it is/was及that/who去掉，句子仍然是正确的。本题考查了强调句型的特殊疑问句。What 在句子是主语。句意：我想知道是什么让他如此难过。