Everyone had an application form in his hand,but no one knew which room (to send it to).请问括号里的部分做什么成分啊?另外逗号后边的整句话是什么结构?

问题描述:

Everyone had an application form in his hand,but no one knew which room (to send it to).请问括号里的部分做什么成分啊?另外逗号后边的整句话是什么结构?

括号里的是动词不定式做定语,修饰room
后面半句的意思是:但没人知道应当把它送到哪个房间.