on one's guard? 警惕,提防

nothing but? 只有,只不過

now and then ? 時而,偶爾

off and on? 斷斷續(xù)續(xù),間歇地

off duty? 下班

on a large/small scale? 大/小規(guī)模地

on account of? 由于

on(an/the) average?? 平均,通常

on behalf of? 代表

on board? 在船(車/飛機(jī))上

on business? 因公

on condition that? 如果

on duty? 上班,值班

on earth? 究竟,到底

on fire? 起火,著火

on foot? 步行

on guard? 站崗,值班

on hand? 在場,在手邊

on occasion(s)? 有時,間或

on one's own? 獨立,獨自

on purpose? 故意地

on sale? 出售;廉價出售

on schedule? 按時間表;準(zhǔn)時

on second thoughts? 經(jīng)重新考慮

on the contrary? 正相反

on the grounds of? 根據(jù),以……為由