1. Jane hasn’t worn that skirt for one year.

It's been a year since John didn't wear that dress (Đó là 1 năm kể từ lúc John không mặc chiếc váy đó)

2 The students haven’t gone to school for a month.

It’s been 1 month since the student didn't go to school ( Đó là 1 tháng kể từ lúc học sinh không đi học)

3The student last did the work last Monday

The student who worked last Monday is the last student (Sinh viên đã làm việc vào thứ Hai tuần trước là sinh viên cuối cùng)

4 I last saw him three days ago

i haven't seen him for three days.

5They haven’t helped the boy since they knew that he was a bad boy .

they last helped the boy when they knew that he was a bad boy.( lần cuối họ đã giúp cậu bé khi họ biết rằng cậu là một cậu bé hư)

1) Jane hasn’t worn that skirt for one year.

⇒ It's one year since Jane last wore that skirt.

Giải thích :

→ Thì HTHT : " S + have/has not + VPII + for/since thời gian "

⇔ " It’s + time + since + S + last + V2/ed + O "

2) The students haven’t gone to school for a month.

⇒ It's a month since the students last went to school

Giải thích :

→ Thì HTHT : " S + have/has not + VPII + for/since thời gian "

⇔ " It’s + time + since + S + last + V2/ed + O "

3) The student last did the work last Monday

⇒ The students haven't done the work since last Monday.

Giải thích :

⇔ " S + have/has not + VPII + for/since thời gian "

4) I last saw him three days ago

⇒ I haven't seen him for three days . 

Giải thích : 

→ " S + last + V2/Ved + time + ago "

⇔ " S + have/has not + VPII + for/since thời gian "

5) They haven’t helped the boy since they knew that he was a bad boy .

⇒ The last time they helped the boy was before they have known that he was a bad boy.

Giải thích :

→ " S + have/has not + VPII + for/since thời gian "

⇔ " The last time + S + Ved/V2+ was + mốc thời gian/ khoảng thời gian "