-- will you come back from the library Linda?-- In an hour.A. What timeB. How oftenC. Ho

问题补充：

-- will you come back from the library, Linda?

-- In an hour.

A. What time

B. How often

C. How soon

D. How long

答案：

A. What time

B. How often

(答案→)C. How soon

D. How long

解析：What time什么时间；How often多久一次；How soon多久；How long多长。根据答语，一小时后，可知问的是时间长久，故选C。