Choose the synonym of the word in the bracket

I didn't think his comments were very (appropriate) at the time.

This is the (instance) where big, obvious non-verbal signals are appropriate.

When you are in a restaurant, you can raise your hand slightly to show that you need (assistance).

When you see your teacher (approaching) you, a slight wave to attract his attention is appropriate.

It is (impolite) not to say "Thank you" when you are given something.