这堂课的长度是50分钟。

The ___length of the lesson was 50 minutes.

他无法集中精力工作任何一段时间。

He is unable to concentrate on his work for any ___length of time.

我们需要您在晚上7点开始演讲，时长为一小时。

We will need you to start the talk at 7:00 p.m. with a ___length of one hour.