1. zealous pursuit
2. inadvertently left
3. exorbitant prices
4. combative workers
5. belligerent attitude
Zealous means eager, so idle is mot nearly opposite.
Inadvertently means by mistake, so purposely is the antonym.
The key element here is ex-, which means out of or away from. Exorbitant literally means "out of orbit".
The opposite of combative is cooperative.
The key element in this word is the root belli-, which means warlike. The synonyms are hostile and ungracious, so the antonym is reasonable.