When a fire _____at the National Exhibition in London, at least ten priceless paintings were completely destroyed.
A、broke off
B、broke out
C、broke down
D、broke up
【正确答案】：B
【题目解析】：break out意思是“（战争、疾病）的突然发生”，符合句意。break off意思是“中断、绝交”；break down意思是“抛锚、出故障”；break up意思是“打碎、分解”。
