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【举一反三】 “祈使句＋and＋陈述句”可以与if引导的条件状语从句或非谓语动词进行相互转化。 【即时巩固】 句型转换 Go straight and you will see a flower shop at the crossing. ①＝_______ ______ ______ _____， you will see a flower shop at the crossing. ②＝__________ ________， you will see a flower shop at the crossing. 【答案】①If you go straight ②Going straight 2．The patent was given in 1876, but it was not until five days later that Bell sent his first telephone message to his assistant Watson. 贝尔于1876年获得专利证书，但是直到五天后贝尔才发出他的第一个电话信息给他的助手沃特森。 句型提炼： It is/was not until＋被强调部分＋that＋其他 该句用了“not…until…”的强调句结构，此句型中只用until，不用till。主句中的否定词not要提出来，放在until之前一起强调，that后面的从句要用肯定句，不能再用否定句。 【句型剖析】 It was not until the professor came that they set about discussing the problem. 直到教授来了，他们才开始讨论这个问题。 【易错点津】 not until置于句首时，要用部分倒装句型，这时要注意从句不倒装，只倒装主句。 Not until we pointed out their fault to them did they realize it. 直到我们向他们指出了他们的错误，他们才意识到。 【即时巩固】 句型转换 The villagers didn't realize the importance of protecting the river until the fish died out. ①＝It was ________ ________ the fish died out ________ the villagers realized the importance of protecting the river. | 
