I'm a musician,________?为什么填aren't I

I'm a musician,________?为什么填aren't I
(1)Mr.Green _____ China for two years.为什么填has been in
(2)When I came in,he was helping Tom _____ the watch.为什么填mend
(3)My uncle has just _____ abroad.He won't come back this month.为什么填gone
(4)Yesterday I went to the train station _____ my uncle.为什么填to meet