The fire must have _____________ after the staff had gone home.

The fire must have _____________ after the staff had gone home.
A、broken out
B、broken down
C、broken in
D、broken through
【正确答案】：A
【题目解析】：break out爆发；突发；break down崩溃；分解；分类；break in打断；闯入；break through突破；突围；有重要创见。句意：这场火灾一定是员工们回家后发生的。