He is never behind with [in] his work.

他工作从不拖拉。

He was behind in [with] his rent.

他拖欠了房租。

He helped a classmate who was behind with his homework.

他帮助一位没有按时完成作业的同班同学。

2 . be behind in doing sth 做某事不落在后面。如：

The boy is behind in handing in homework.

这孩子没能按时交家庭作业。

He was never behind in offering suggestions.

他提建议从来不落在别人后面。

3 . from behind 从后面。如：

He held her from behind.

他从后面抱住她。

They attacked us from behind.

他们从后面攻击我们。

注：有时 behind 是介词，其后可接宾语。如：

He came out from behind the door.

他从门后出来。

4 . fall [drop ] behind 落在后面。如：

I’ve fallen behind in work. 我工作落后了。

Some students dropped behind in their studies.

有的学生在学习上落在后面。

5 . leave sth behind 走后留下某物。如：

What have we left behind?

我们走后留下什么了?

He left his umbrella behind.

他离开时没有把雨伞带走。

6 . stay [remain ] behind 留下，在别人后面留下。如：

He alone remained behind.

只有他一个人留下没走。

I had to stay behind after school.

放学后我还得留在学校。