39. A huge forest fire ______ after the lightning struck, but luckily no one died or got hurt.

A．broke out

B．broke up

C．broke down

D．broke off

鼠标用久了,使用中光标移动不够灵活,最可能的原因是()。

A．鼠标与主机连接线脱落

B．灰尘附到橡皮球和转轮上,容易积垢

C．鼠标按键下面的弹簧老化

D．操作者把持鼠标不稳