Choose the correct word. Are there any similar idioms in your language?

1 Lots of people are off sick with the flu in our college. They're dropping like ...

2 You look a little off ... today. Are you tired?

3 Matt's really under ... He's got a terrible cold.

4 Take it easy for a few days and you'll be back on your ... in no time.

5 You should take some vitamins if you're feeling a bit ... down.