---do you usually read English in the morning?---About half an hour.A. WhenB. What timeC.

问题补充：

---do you usually read English in the morning?

---About half an hour.

A. When

B. What time

C. How many

D. How long

答案：

A. When

B. What time

C. How many

(答案→)D. How long

解析：疑问词辨析。When什么时候；What time几点钟；How many多少个；How long多长。根据答语About half an hour大约半个小时，可知上文提问时间长短，故用how long来提问。选D。