Question

We traveled over night to Pairs and arrived ________ 5 o'clock _______ the morning.

1. A.
   on, on
2. B.
   at, in
3. C.
   at, on
4. D.
   in, in

Answer 1

B
在某时某刻前面用介词at；在上午、下午、晚上用in。题中为“上午5点钟”，故选B。