______ over and over again, but he still couldn't understand.

______ over and over again, but he still couldn't understand.

1. A.
   Having explained
2. B.
   Having been explained
3. C.
   Explaining
4. D.
   It had been explained

______ over and over again, but he still couldn't understand.

       A.Having explained              B.Having been explained      

       C.Explaining                 D.It had been explained

______ over and over again, but he still couldn’t understand.

I explained over and over again in order to try not to make myself ________．

1. A.
   understood
2. B.
   understand
3. C.
   misunderstand
4. D.
   misunderstood