optimistic

a.乐观的，乐观主义的

oppressed, oppression, oppressive, oppressor, opprobrious, opprobriously, opprobrium, ops, opt, opt out of, optic, optical, optical art, optical illusion, optically, optician, optics, optimal, optimism, optimist, optimistically, optimization, optimize, optimum, option, optional, optometrist, opulence, opulent, opus, or, or else, or rather, or so, oracle, oracular, oral, orally, orang-utan, orange,