Соотнести фиксированные фразы с их значением. Кидаю жалобы за спам и ответы не по теме. Берегитесь. ​

off-chance - just in case

on second thoughts - after re-consideration

on a whim - impulsively

on a budget - with a limited amount  of money

on principle - due to a belief

on one's own - independently

on target - as planned

on duty - working

on purpose - intentionally

on condition that - only if