`1.` Where did you buy this dictionary `?`

`+` where : ở đâu, nơi nào

`2.` How long did it take her to do the housework `?`

`+` how long : bao lâu

`3.` When did they return to America `?`

`+` when : khi nào, lúc nào

`4.` What time did Nam leave home `?`

`+` what time : mấy giờ

`+` at + giờ

`--------------`

`-` QKĐ :

`( ? )` Wh / h + did + S + V-inf ?

$#Ribee$

`1`. Where did you buy this dictionary?

`->` Where...?: Ở đâu?

`2`. How long did it take her to do the housework?

`->` How long...?: Bao lâu?

`3`. When did they return to America?

`->` When...?: Khi nào?, Bao giờ?

`4`. What time did Nam leave home?

`->` What time...?: Mấy giờ?

`------------------`

`***` Câu hỏi ở thì QKĐ:

   (Wh) + Did + S + V-inf?