481 once and for all =once and forever永遠(yuǎn)地 all at once 立即,馬上 once in a while 立即,馬上

　　once in a while 偶爾

　　for once 就這一次

　　482. by oneself 獨自

　　483. operate on sb. 給某人做手術(shù)

　　operation n. come/ go into operation開始運轉(zhuǎn)

　　put/bring sth. into operation 使投產(chǎn),運轉(zhuǎn)

　　484. be of the opinion 持有的看法

　　485. in ones opinion 按某人的看法

　　486. be opposed to 反對

　　487. be opposite to 與相反的

　　488. in order合適的,恰當(dāng)?shù)?/p>

　　in order 井井有條,處于良好狀態(tài); out of order出毛病,發(fā)生故障

　　489. made to order 定做的

　　490. originate in/from起源于,由..引起

　　491. on the outskirts 在城郊

　　492. oweto 把歸于

　　493. on ones own 單獨

　　494. of ones own某人自己的

　　495. keep pace with 跟齊步前進(jìn)

　　496. go to great pains=take pains 下功夫,努力

　　497. part with 舍棄,賣掉

　　498. participate in 參加

　　499. particular about 講究,挑剔

　　500. in particular 特別是,尤其