+ 1) My classmate improved his English in the USA.
-- 2) My classmate didn't improve his English in the USA.
Yes/No 3) Did your classmate improve his English in the USA?
Who 4) Who improved his English in the USA?
Alt 5) Did your classmate improve his English in the USA or in Germany?
Tag 6) My classmate improved his English in the USA, didn't he/she?