observe vt.遵守;看到;说;
obtain vt.获得,得到,买到;
obvious a.明显的.,显而易见的;
obviously ad.明显地,显然地;
occasion n.场合,时刻;时机;
occasional a.偶然的;临时的;
occasionally ad.偶然;非经常地;
occupation n.占领,占据;职业;
occupy vt.占领;占,占有;
occur vi.发生;出现,存在;
occurrence n.发生,出现;事件;
ocean n.海洋;洋;
Oceania n.大洋洲