nowandthen?nowandagain?onceinawhile

now and then?now and again?once in a while?

1. now and then?

now and thenHe looks at me now and then.

2. now and again?

now and againnow and thenI now and again forget to bring my umbrella.?

3. once in a while?

once in a while?We should exercise once in a while to keep healthy.?

"now and then"?"now and again"?"once in a while"?