opportune

adj. 合适的，适当的

operation, operational, operations room, operative, operator, operetta, ophthalmic, ophthalmic optician, ophthalmologist, ophthalmology, ophthalmoscope, opiate, opine, opinion, opinion poll, opinionated, opium, opossum, opp, opponent, opportunely, opportunism, opportunist, opportunistic, opportunity, oppose, opposed, opposite, opposition, oppress, oppress-ively, oppressed, oppression, oppressive, oppressor, opprobrious, opprobriously, opprobrium, ops, opt,