[命题点感悟]

　　单句语法填空

　　①(2017·全国卷Ⅰ)Before getting into the car, I thought I had learned the instructor's orders, ________ once I started the car，my mind went blank.

　　解析：but/yet　此处表示"我认为我已经明白了教练的指令，但是车一启动，我的脑子却一片空白"。由此可知，前后分句之间是转折关系。

　　②(2017·全国卷Ⅲ)I have grown not only physically, ________ also mentally in the past few years.

　　解析：but　not only ...but also ...是固定短语，意为"不但......而且......"。

　　③(2016·全国卷Ⅰ)Every day he makes sure that fresh vegetables ________ high quality oil are used for cooking.

　　解析：and　根据语境可知，新鲜的蔬菜与高品质的油二者之间为并列关系。

　　④(2016·全国卷Ⅱ)We can choose between staying at home and taking a trip.If we stay at home, it is comfortable ________ there is no need to spend money.

　　解析：and　第二句句意：我们如果待在家里，会感觉舒适，还不花钱。根据句意可知，"comfortable"与"no need to spend money"之间是并列关系，故用and。

　　⑤(2015·广东高考)One day, the cow was eating grass ________ it began to rain heavily.

　　解析：when　be doing sth.when ..."正在做某事，这时突然......"。

状语从句 　　1．时间状语从句

　　(1)when, while与as引导的时间状语从句

连词 从句谓语动词 用法 when 延续性动词、非延续性动词 从句的动作和主句的动作可以同时发生，也可以先后发生 while 延续性动词 从句的动作与主句的动作同时发生 as 延续性动词 强调主从句动作相伴发生，可译为"一边......一边......；随着" 　　

　　Metals expand when they are heated.

　　金属受热时膨胀。

While/When I was reading, he came in.