To buy a ticket,you ___line up at this window（must mustn't与have to选一）急!
问题描述：
To buy a ticket,you ___line up at this window（must mustn't与have to选一）急!
答
选have to
意思是：要买票的话，你不得不在这窗口排队。
must 表主观的必需，也就是说主语有这方面的需要
比如：We must find a good method to learn English.
have to 表客观必需，也就是说迫于外部的压力
比如：I have to look after my little sister because mom is out.
答
have to