I believe ( ) he told me because he is a man who never tells a

I believe ( ) he told me because he is a man who never tells a lie.
A、what
B、that
C、all what
D、which
【正确答案】：A
【题目解析】：根据含义判断，what引导宾语从句，句子含义是我相信他说的一切，因为他从不撒谎。