I can’t understand is         he wants to change his mind.

A．That, what          B．That, why        C．What, what        D．What, why

________ I can’t understand is ________ he wants to change his mind.

________ I can't understand is ________ he wants to change his mind．

1. A.
   That, that
2. B.
   Which, how
3. C.
   What, what
4. D.
   What, why

________ I can't understand is ________ he wants to change his mind.

[　　]

________ I can't understand is ________ he wants to change his mind.

[　　]