A、  B、  C、  A问句以疑问词how long来询问一段特定的时间。问的是等了多久，(A)回答等了不到一个小时，因此是正确答案。

How do you get to your office?
(A) I drive myself.
(B) I was here about forty-five minutes ago.
(C) I work downtown.

How long have you been waiting?
(A) Less than an hour.
(B) I’ve worked here since my graduation.
(C) I don’t mind waiting.