高一英语同步课程
《完形填空之词语辨析》麻雪玲
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老师传授典型题详细办法
教学生举一反三
一题多解、一题巧解
错题本
错题追踪复习
听课中的错题能自动加入错题本
课后可方便复习及导出错题本
网络答疑
课程互动性强
在线互动问答
数理化英快速答疑
课后练习
经典例题课后练习
老师针对课堂中的经典例题
为学生推送同类型题，掌握解题方法
In order not to cause something dangerous to happen, the teacher may fill some white vinegar(白醋, some cooking oil(香油),some alcohol(白酒) in the tubes.
3. once 是连词，作“ 一旦……就……”讲。
(1) Once she arrives, we can start.
(2) Once you realize it, you will study hard.
(3) Once seen, it can never be forgotten.只要见过一次就难以忘怀。
注意once 一般和现在时连用。
4.unless是连词，相当于if …… not ……
(1) He will not come unless his homework is finished. == He will come if his homework is finished.
(2)You will be in trouble unless you follow my instruction. == You will not in trouble if you follow my instruction.
unless 和 not …until 的区别
unless 引导从句时多强调条件，而not …… until 句型则强调时间。Unless 连接的主从句的时态一般是主句是将来时而从句现在时。not …… until 连接的主从句中可以使用多种时态。
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