过去进行时铺垫故事的背景

精讲课笔记随视频锁定

右侧笔记支持独立滚动。边听名师连读拆解，边对照右侧的语法事实与统计数据笔记。

故事背景铺垫^{(when/while/as 当...时)}	当 A 发生的时候出现了 B
When they were sleeping,	a thief sneaked in.
While he was reading the letter,	he heard a knock at the door.
While my friend, George, was reading in bed,	two thieves climbed into his kitchen. §
When my husband was going into the dining room this morning,	he dropped some coins on the floor. §

当 A 时发生了 B	当B时发生了 A
While/When/As two detectives were keeping guard at the door, two others opened the parcel.	Two detectives were keeping guard at the door, when two others opened the parcel.
While/As/When they were sleeping, a thief sneaked in.	They were sleeping, when a thief sneaked in.
When the plane arrived, some of the detectives were waiting inside the main building while others were waiting on the airfield.	The plane arrived, While/As/When some of the detectives were waiting inside the main building While/As/When others were waiting on theairfield.
He was reading a book when/as/while his wife was cleaning the house.	^{when 强调了后一个事件（妻子清扫房子）发生时前一个事件（他读书）正在进行。这种使用方式表示两个事件有一定的顺序和因果关系。} ^{while 强调两个动作的同时性。"while"用来引起一个附加动作，表示两个动作在同一时间段内持续进行。}^as^{表示两个事件之间更强的同时性，并且没有明确的因果关系。这里的重点是强调两个动作同时发生。}