`1`.We haven't seen her since Christmas Day

`\rightarrow` Thì HTHT ( CPĐ ) : S + haven't / hasn't + V3 / PII

`\rightarrow` Đặc điểm nhận dạng : since

`2`.This is the first time I have eaten this kind of food

`\rightarrow` This is the first time + S + have / has + V3 / PII : Lần đầu tiên làm gì

`3`.It has rained for an hour

`\rightarrow` Thì HTHT : S + have / has + V3 / PII 

`\rightarrow` Đặc điểm nhận dạng : for

`4`.The last time I visited my grandfather was two months ago

`\rightarrow` The last time + S + Ved / V2 + was + time : Lần cuối cùng làm gì

`5`.I began studying English three years ago

`\rightarrow` S + started / began + V-ing / to V : Bắt đầu làm gì

`6`.It's nearly five years since my brother last saw his best friend

`\rightarrow` It's + time + since + S + last + V2 / Ved : Đã là ... kể từ khi

`7`.How long have you learnt English ?

`\rightarrow` Thì HTHT ( CNV ) : Have / Has + S + V3 / PII ?

`\rightarrow` How long dùng để hỏi về bao lâu

`8`.We have lived here for fifteen years

`\rightarrow` Thì HTHT : S + have / has + V3 / PII

`\rightarrow` Đặc điểm nhận dạng : for

`\text{@ TheFox}`