Question

________ ! There's a train coming．

1. A.
   Look out
2. B.
   Look around
3. C.
   Look forward
4. D.
   Look on

Answer 1

A
look out相当于be careful；take your step；意为“当心，注意”；look around“环顾四周”；look forward“盼望；指望”：look on“观看，旁观”。由There's a train coming可知，look out在此是唤起注意的意思”。