– have you been skating?– For five hours.A. How oftenB. How soonC. How farD. How long

问题补充：

– have you been skating?

– For five hours.

A. How often

B. How soon

C. How far

D. How long

答案：

A. How often

B. How soon

C. How far

(答案→)D. How long

解析：答语为for five hours表示段时间，故用how long来提问。