问题
选择题
--- What on earth are the police busy with?
--- They have been investigating how the train crash __________.
A．came out
B．came across
C．came about
D．came up
答案
C
题目分析：句意为：----警察们究竟在忙什么呢？ ---他们正在调查这次火车相撞的原因（是怎么发生的）. come out 出版，发行，发现； come across偶然遇到，碰到；come about 发生，产生；come up 想出，提出。故答案应为C。