The computer system suddenly while he was searching for information on the Inter

本题考查动词短语语意的区别。句意为：“正当他在网上查信息的时候，电脑系统突然瘫痪了。”break down：(of a machine or vehicle)to stop working because of a fault(机器或车辆)出故障、坏掉。break out：(of war, fighting or other unpleasant events)to start suddenly(战争、打斗等不愉快事件)突然开始。break up：(1)to come to an end结束；(2)to go away in different directions解散，散开；(3)to become very weak变得虚弱、垮掉。break in：to enter a building by force强行进入；破门而入。