问题补充：
He really can’t understand he said was wrong.
A. what
B. how
C. that what
D. why what
答案：
A. what
B. how
C. that what
(答案→)D. why what
解析：
试题分析:考查宾语从句。分析结构可知understand后是宾语从句，he said部分在从句中做主语,因为said是及物动词，所以要用what来做said的宾语，排除B选项。因为引导宾语从句时that可以省略，所以A、C选项意思相同，故正确答案是D。句意：他真的不理解为什么他说的话是错误的。
