length前加什么介词

前面加介词in，例如：

1、Each class is 45 minutes in length.每一节课为45分钟。

2、The river is 300 miles in length.这条河长300英里。

3、Her novels vary in length.她的小说篇幅长短不一。

4、The movie is nearly two hours in length.这部电影时长近两个小时。

5、His film， over two hours in length， is a subtle study of family life.他这部片长逾两个小时的电影对家庭生活进行了巧妙的剖析。

加介词at，中文意思是，最后，终于详细地

At length the woman hoped that God was about to grant her desire.最后，女人希望上帝会满足她的愿望。

Mr. Perks questioned them at length to establish their bona fides.

珀克斯先生详细地询问他们以确定其诚意。