I haven’t gone to school for 4 months because of COVID-19.

`→` It is 4 months since I last went to school because of COVID-19.

`→` I last went to schoold 4 months ago because of COVID-19.

`→` The last time I went to school was 4 months ago.

* Giải thích các bước làm :

S + last + V quá khứ + thời gian ( 2 days ago/in 2010)

= The last time + S + V quá khứ + was thời gian 

= S + have/has not + VPII + for/since thời gian

= It is + Thời gian + since + S + last + V quá khứ

I haven’t gone to school for 4 months because of COVID-19.

- S + haven't/hasn't + VpII + ... + for + time/since + time

`->` It is 4 months since I last went to school because of COVID-19.

- It is + time + since + S + last + V2/V-ed + ....

`->` I last went to school 4 months ago because of COVID-19.

- S + last + V2/V-ed + ... + time + ago/when + time

`->` The last time I went to school was 4 months ago.

- The last time + S + V2/V-ed + ... + was + time + ago