she went out to see what Aishappening B is happend Cwas happ

She went out to see what (C.was happening).
她出去看发生了什么事情.
括号部分中是宾语从句,时态要和主句一致,不可能是现在时态.所以A项is happening和B项is happend就先排除了.happen是不及物动词,不可能有被动语态的形式,所以D项was happened也是错误的.
C项是过去进行时态,正确.