Question

---You look pale,what troubled you?

---I ________ mymissing friend.

1. A.
   amthinking about
2. B.
   wasthinking about
3. C.
   hadthought about
4. D.
   will thinkabout

Answer 1

A
从对话中可知动作发生在现在，故用现在进行时，意为“我正在想我失去的朋友”。