they. (laugh).loudly when she entered the room是不是had laughed

they. (laugh).loudly when she entered the room是不是had laughed
they. (laugh).loudly when she entered the room
是不是had laughed

they. (laugh).loudly when she entered the room是不是had laughed
个人意见.
应该是were laughing.她进屋的时候他们正在大笑.

were laughing
因为时间状语从句是有固定句式的
（1）过去式+when+过去式
（2）过去进行时+when+过去式
如果是had laughed 则表示他们笑发生在她进入房间之前 语义不通、