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must have been working all the 。 think the stones can prevent illness and keep people 認(rèn)為這些石頭可以預(yù)防疾病 , prevent 作及物動(dòng)詞,可直接帶賓語(yǔ),表示“阻止,阻撓”的意思;常構(gòu)成: preventfrom 表示“保護(hù)??不受??侵襲”; prevent doing ,在主動(dòng)語(yǔ)態(tài)中 from 可以省略,被動(dòng)語(yǔ)態(tài) These regulations are intended to prevent He prevented the boy from climb