I:Change the following sentences into Yes/Nó questions

`15.` Have you been to Sapa several times?

`-` Thì HTHT (nghi vấn): Have/has + S + Ved/3...?

`16.` Are the girls with a shawl on their heads members of the Thai?

`-` Thì HTĐ (nghi vấn): Am/is/are + S + adj/N...?

`17.` Can we find terraced fields in the northern mountainous regions?

`-` Can + S + V-inf...?

`18.` Did they build their houses on stilts to prevent flooding from tides or storms?

`-` Thì QKĐ (nghi vấn): Did + S + V-inf...?

`19.` Are the Tay the earliest known minority in Viet Nam?

`-` Thì HTĐ (nghi vấn): Am/is/are + S + adj/N...?

`-` So sánh nhất với tính, trạng từ ngắn: S + V + the + adj/adv + -est...

`20.` Is the population of the Tay ethnic group about 1.7 million?

`-` Thì HTĐ (nghi vấn): Am/is/are + S + adj/N...?

`#vu0000`