问题补充：
-- will your English teacher come back?
-- In two days.
A. How often
B. How long
C. How soon
D. How far
答案：
A. How often
B. How long
(答案→)C. How soon
D. How far
解析：A. How often多久一次，表示频率；B. How long 多长时间或是距离 ；C. How soon 多久，一般用于将来时态中； D. How far多远的距离；句意：你的英语老师什么时候回来？两天后。故选C.
