UNTIL和BEFOREI developed very slowly and it took nearly two hunred years before I as built as a an analytical machine by Charls Babbage.为什么用before不用until?

not.until 与not.beforeI could not finish the homework________.A.until he has come B.before he cameC.when he comes D.by he had come选那一个?为什么?着重介绍not until 和not..before的区别, UNTIL和BEFOREI developed very slowly and it took nearly two hunred years before I as built as a an analytical machine by Charls Babbage.为什么用before不用until? not until not beforei knew nothing about the accident ___my friend told me yesterday?答案until但是能不能用before说明理由 until...和not until... until和not until的区别 not until 和until的区别 until和not until有什么区别 not until 和 until的区别 until和not until的用法 not until用法和句子 until 和till 的用法 until和before 的区别. Until和Till的区别 till和until的区别? until和till的区别. unless和until的区别, until和till的区别 since和until的区别