3/ I haven’t gone to school for 4 months because of covid-19.
Công thức:S + have/has + not + VpII + for + time
-> The last time I went to school was 4 months ago because of Covid-19
Công thức:The last time + S + V-ed + was + time + ago
-> I last went to school 4 months ago because of Covid-19
Công thức: S + last + V-ed + time + ago
-> It is 4 months since I last went to school because of Covid 19
Công thức: It is + time + since + S + (last) + V-ed