一Mary，you look confused．Have you made sense of the passage we are talking about?
一Yes，I      another problem just now

1. A.
   have thought of
2. B.
   was thinking of
3. C.
   thought of
4. D.
   had thought of

一Mary，you look confused．Have you made sense of the passage we are talking

about?

一Yes，I      another problem just now.  

       A．have thought of   B．was thinking of    C．thought of        D. had thought of

一Mary，you look confused．Have you made sense of the passage we are talking about?

一Yes，I      another problem just now.  

       A．have thought of   B．was thinking of   C．thought of    D. had thought of