could也能表示過去的一般的允許：

　　On Sundays we could(=were allowed to)stay up late.

　　星期天晚上我們能到較晚才睡。

　　當(dāng)某一具體行為獲準(zhǔn)并付諸實(shí)施時(shí)，就必須用was/were allowed代替could：

　　I had a visa so I was allowed to cross the frontier.

　　我有簽證，所以我被允許越過邊界。

　　couldnt的用法比could要稍為廣泛一些：

　　We couldnt bring our dog into the restaurant.

　　我們不能把狗帶進(jìn)飯館里。

　　與此相反的意思應(yīng)當(dāng)用allow表示：

　　We were allowed to bring

　　允許我們把狗帶進(jìn)，

　　如欲使用完成時(shí)和被動(dòng)語態(tài)，則必須用 allowed：

　　Since his accident he hasnt been allowed to drive.

　　自從他出了車禍以后就不允許他再開車了。

　　As a child he had been allowed to do exactly what he liked.

　　他小時(shí)候，容許他愛干什么就干什么。