will you go back from Hong Kong?-In 3 days.A. How long B. How soon C. How often

问题补充：

will you go back from Hong Kong? ---In 3 days.

A. How long B. How soon C. How often

答案：

解析：句意：你多久以后从香港回来？三天后。How long多久；How soon 多久以后； How often多久一次。所以选B。