1,they bought a lot of bread (yesterday)
⇒When did they buy a lot of bread?
2,the Thai live on farming( in the mountainous) areas
⇒ Which areas do the Thai live on farming?
3,there are (54) ethnic groups in VN ( bạn viết nhầm đề một chút nhé)
⇒How many ethnic groups are there in Vietnam?
4,he was born in a (small town)
-> Where was he born?