A、  B、  C、  C本句是询问到办公室所花时间的How疑问句。How long…可理解为对时间段的提问。

Why was Francis sent to Germany last week?
(A) Ten cents per call.
(B) That’s a weak excuse.
(C) He attended a conference.

How long does it take to reach your office?
(A) On the ninth floor.
(B)lt’s 12 o’clock.
(C) Around an hour.