2 Complete each sentence with the proper form of the expression in brackets. 用括号中所给短语的适当形式补全句子。
(1) As he tapped “send”, the message (quickly disappear) into the digital world.
(2) When we (watch a film) in the cinema, an old man’s smartphone suddenly rang.
(3) Tom (stop working) until a low battery warning appeared on his laptop screen.
(4) While the teacher was writing on the smartboard, the students (take notes) on their tablets.
(5) Before the robot (start dancing), the girl tapped the “GO” button on its arm.
(6) As soon as Mary (connect) her smartphone to the Wi-Fi messages popped up (突然出现) from her group chat.
D

(1) quickly disappeared (2) were watching a film (3) didn’t stop working
(4) were taking notes (5) started dancing (6) connected

【分析】本题考查英语动词时态的正确运用，需结合句子中的时间连词（when、while、until、as soon as、before）及主从句动作的先后、进行状态，确定括号内短语的适当形式：一般过去时用于描述过去完成的动作，过去进行时用于描述过去某个时刻正在进行的动作，until需搭配not构成“not...until”结构表“直到...才”。
【解析】
(1) 句中as引导的时间状语从句动作tapped是一般过去时，主句动作disappear也发生在过去，用一般过去时，副词quickly修饰动词，故填quickly disappeared。
(2) when引导的时间状语从句，主句动作rang是一般过去时，从句表过去某时刻正在进行的动作，用过去进行时，主语为we，故填were watching a film。
(3) 句中until表“直到...才”，需用否定式，结合appeared（一般过去时），主句用一般过去时的否定结构，故填didn’t stop working。
(4) while引导的时间状语从句，从句是过去进行时，主句表同时正在进行的动作，用过去进行时，主语为the students，故填were taking notes。
(5) before引导的时间状语从句，动作发生在过去，用一般过去时，故填started dancing。
(6) as soon as引导的时间状语从句，主句动作popped是一般过去时，从句用一般过去时，故填connected。
【答案】(1) quickly disappeared (2) were watching a film (3) didn’t stop working (4) were taking notes (5) started dancing (6) connected
【知识点】一般过去时、过去进行时、时间状语从句
【点评】本题聚焦时间状语从句中时态的搭配规则，是英语时态的基础应用题型，需掌握不同连词对应的时态要求，难度适中。
【难度系数】0.5