1 we haven't seen him since Christmas

→ S + have / has + VPII + since + 1 mốc thời gian / thì QKĐ

2 this is the fisrt time i have ever eaten this kind of eaten

→ this is the first time + S + have / has + VPII

3 it has rained for an hour

→ S + have / has + VPII + for + 1 khoảng thời gian

4 thel ast time we visited my grandfather was two months ago

→ the last stime + S + VPII + somebody / something + was + thời gian + ago

5 i began studying English 3 years ago

→ began + V-ing

6 it's five years since my brother last saw his best friend

→ It's + thời gian + since + S + ( last ) + V-ed / v2

7 how long  have you studied english ?

→ how long + have / has + S + VPII