The puter system suddenly while he was surfing the Internet.
A. broke up
B. broke out
C. broke in
D. broke down
网友回答
A. broke up
B. broke out
C. broke in
(答案→)D. broke down
解析：短语辨析。A关系破裂；分解；B爆发；C闯入；D机器坏了，身体垮了；分解；抛锚；崩溃；结合句意可知D正确。句意：当他在上网的时候，计算机系统突然就崩溃了。