Bài `4:` 

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

`->` The last time + S + V2/ed + was + .... = S + have/has + not + Vpp

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

`->` S + have/has + not + Vpp + before = This is the first time + S + have/has + Vpp

`3`. It has rained for an hour.

`->` S + started + Ving + thời gian + ago = S + have/has + Vpp + for + khoảng thời gian

`4`. The last time we visited my grandfather was 2 months ago.

`->` The last time + S + V2/ed + was + .... = S + have/has + not + Vpp

1. We haven't seen her since Christmas day.

The last time + S + $V_{QK}$ + khoảng thời gian 

⇔ S + haven't/hasn't + $V_{II}$ + since/for + thời gian.

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

S + haven't/hasn't + $V_{II}$ + before

⇔ This is the first time + S + have/has + $V_{II}$.

3. It has rained for an hour.

S + stared/beganed + V_ing + thời gian.

⇔ S + has/have + $V_{II}$ + since/for + thời gian.

4. The last time we vistied my grandfather was two months ago.

S + haven't/hasn't + $V_{II}$ + since/for + thời gian

⇔ The last time + S + $V_{QK}$ + khoảng thời gian.