“他们是哪个国家的人”的英文

which country are they from?（较中国式）
which country do they come from?（较中国式）
what's their country?（较中国式）
where are they from?(最常用)
where do they come from?（较常用）
what's they nationality?（较书面）

Which country are they come from?
或者
Where are they come from?

Which country do they come from?
Which country are they from?

Where are they come from?
what's their country?

Where are they from?
Where do you come from?

Which country are they from?