-- will you come back?- In an hour.A. How soonB. How oftenC. How longD. How far

问题补充：

-- will you come back? --- In an hour.

A. How soon

B. How often

C. How long

D. How far

答案：

(答案→)A. How soon

B. How often

C. How long

D. How far

解析：A多久 B. 多久一次 C.多长 D. 多远。根据下文，一个小时后。可知上文问的是时间，选A。