Question

---You look so pale.What trouble you?

---I ______ my dead mother.

1. A.
   though about
2. B.
   was thinking about
3. C.
   have thought about
4. D.
   am thinking about

Answer 1

B
对过去的情况进行描述性的解释，这种解释答了问题的原因，A项答What did you do 的问题。C项没有直接答问题，D项时态表达错误。