问题补充：
The computer system suddenly while he was searching for information on the Internet.
A. broke out
B. broke down
C. broke up
D. broke in
答案：
A. broke out
(答案→)B. broke down
C. broke up
D. broke in
解析：考查短语辨析。句意“电脑闹系统突然失灵了，当他上网找信息时。”A“爆发”；B“出毛病，瓦解，中止，彻底失败”；C“分解，解散”；D“打断，闯入”。故选B。
