on one's mind的意思是什么

造句：

1.  He looked down as if he had something on his mind.

   他低着头，好像有什么心事。

2.  He looks worried and seems to have something on his mind.

    他愁眉不展，似乎有心事。

3. She was depressed and silent, and looked as if she had something on her mind.

   她郁郁寡欢，沉默不语，看样子像有什么心事似的。

4. Xiaofang is worried all day. She must have something on her mind.

   小芳整天愁眉不展的,一定有什么心事。