--- Have you thought of the topic for the composition?　　　　---Not yet I it very carefully

问题补充：

--- Have you thought of the topic for the composition?

---Not yet, I it very carefully, but I haven’t decided.

A. will consider

B. have been considering

C. had considered

D. was considering

答案：

A. will consider

(答案→)B. have been considering

C. had considered

D. was considering

解析：I haven’t decided yet说明一直在考虑，还没决定，故选B。