—Whatareyoubusywithrecently?  —Wehavebeenlookingintoho...

问题详情：

 —What are you busy with recently?

   —We have been looking into how the machine breakdown __________.

   A. came out           B. came about          C. came down                     D. came up

【回答】

B

知识点：动词

题型：选择题