---What are you busythese days?----Nothig muchA. doB. to doC. doingD. done

问题补充：

---What are you busythese days?

----Nothig much

A. do

B. to do

C. doing

D. done

答案：

A. do

B. to do

(答案→)C. doing

D. done

解析：考察固定结构be busy doing 忙着做某事。句意:这些天他们正在忙着做什么?故选C。