---What do you think of my answer to the question?
----Sorry, What’s that? I _______ about something else.

---What do you think of my answer to the question?

----Sorry, What’s that? I _______ about something else.

A．am thinking        B．was thinking        C．had thought        D．thought

---What do you think of my answer to the question?
----Sorry, What’s that? I _______ about something else.

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