21. Mary __________ lunch when they came. prepared was preparing prepares is preparing 22. Jane ___________ her room while Peter was having a bath. tidy tidied was tidying was tyding 23. When __________? An hour ago. does he call did he call did he called was he calling 24. She was waiting for the bus when her mobile ___________. ring rings rang was ringing 25. We _________ a piano lesson at 5 o'clock yesterday afternoon. have had were having was having 26. They _________ cooking and then went out. finishes are finishing finished were finishing 27. Peter __________ tennis when it started raining. playing was played was playing play 28. The children _________ TV while Mum was reading a magazine. watched was watching were watching watches 29. Stella was making dinner when the lights __________ out. goes go went were going 30. It ___________ yesterday. did rain didn’t rain didn’t rained wasn’t raining

$\text{21.}$ was preparing 

$\text{22.}$ tidied 

$\text{23.}$ did he call ( dấu  hiệu : an hour go ) 

$\text{24.}$ rang 

$\text{25.}$ were having ( dấu hiệu : at 5 o'clock yesterday afternoon ) 

$\text{26.}$ finished ( vế sau chia QKĐ nên vế trước cũng chia ) 

$\text{27.}$ was playing 

$\text{28.}$ were watching 

$\text{29.}$ went 

$\text{30.}$ didn't rain ( dấu hiệu : yesterday ) 

→ QKTD + when + QKĐ 

→ QKĐ + while + QKTD 

→ QKTD + while + QKTD

→ S + was/were + V-ing + O 

→ S + Ved/cột 2 + O 

$#Keisha$

21 a⇔vì mệnh đề QKTD thì 1 mệnh đề quá khứ ,còn lại quá khứ tiếp diễn

22 c⇔vì while là dùng cho hành động cùng xảy ra một lúc,mà âm cuối y ko bỏ 

23 b⇔vì ago QKD ,trợ động từ did+ S+v ko chia

24 c⇔vì mệnh đề kia QKTD rùi,còn lại QKD

25 c⇔vì yesterday QK nhưng tại một thời điểm xác định trong QK là QKTD nên we vs were

26d⇔vì QK nên they vs were

27 d⇔vì mệnh đề kia QK rùi ,còn lại là QKTD be v ing QK

28d⇔vì while là cùng lúc nên children số nhiều vs were

29c⇔vì mệnh đề kia QKTD rùi ,còn lại QKD ,nhưng chỉ sử dụng khi có when

30 b⇔vì yesterday QKD nên trợ động từ did+v ko chia

mk xin hay nhất vs 

làm ơn mà