Each sentences has a mistake .Find and correct it .
1.She has been there since -> for two months
since+ mốc thời gian
for + khoảng thời gian
2.He said he is -> was watching TV then
=> câu gián tiếp
3.I have bought a new computer who -> which is made in Japan
mệnh đề quan hệ
4.You go -> went to school by bike yesterday ,didn't you ?
yesterday -> thì QKD