他们来自哪里可以说：Where are they from？或Where do they come from?例句：Where are they from？——They are from China.
回答是I'm from...或I come from...
例句1
——Where are you from？
——I'm from China.
例句2
——Where are you come from？
——I come from England.
例句3
——Which country are you from？
——Italy.
例句4
——Which city are you from？
——Shanghai.