They discovered the cause of the fire accidentally.They discovered it_____

问题描述:

They discovered the cause of the fire accidentally.They discovered it_____
(a)by chance (b)chancily (c)fortunately (d)luckily 见新概念二第53课多项选择题

(a)by chance
针对灾难,不适用另几个请告诉我其他几个分别为什么意思,谢谢a 碰巧b 没有这么用的c 幸运地d 幸运地