Fill in the gaps with the appropriate particles.
1. I've had this toy train since I was a child, but now it's falling ... .
2. He had to stay in hospital for two weeks, so he fell ... his lessons.
3. Have you fallen ... Helen? She didn't talk to you this morning.
4. There is something wrong with George. He's falling ... his work.
5. Our car is falling ... . We should replace it soon.