________thatallmountainroadswereclosed.
A.So became the dangerous weatherB.So dangerous did the weather becomeC.So dangerous became the weatherD.Dangerous the weather became so在线课程B
解析：
考查倒装句。So+ 形容词或副词放在句首使用部分倒装，借助于助动词，故选B。句意：天气变得如此的危险以至于所有的山路被关闭了。