C1:It has 2 years since I bought the computer.

C2:It is 6 months since I was 12 years old.

C3:It is three years since I have seen Bill.

C4:It is two months since Tom has smoked a cigarette.

C5:It is two years since he left the country.

C6:It's is 20 minutes since the telephone rang.

C7:It is 10 years since I played football.

C8:It's over six months since she had a swim.

C9:It hasn't snowed here for 3 months.

C10:I haven't had a haircut for 2 months.

It is 10 minutes since the telephone rang.

It is 5 hours since I played football.

It is 2 years since the last time I have smoked.

It is 4 years since the last time I have played table tennis.

It is 3 hours since I have breakfast.

It is 5 weeks since I was sick.

It is 2 times since the last time I have smoked.

It is 3 secs since the first hit.

It is 4 days since the last time I have kissed her.

It is never since I was born.

CÓ VÀI CÁI BỊ SAI THÌ PHẢI, MÀ HÌNH NHƯ CŨNG KHÔNG CÓ NỮA.