1. He hasn't gone abroad before

2. I haven't tried sushi before

3. They haven't visited the museum before

4. This is the first time I have climbed this mountain

5. This is the first time she has eaten a frog hotpot

6. This is the first time I have been to Vietnam

---------------------------

This is the first time + S + have/has + VpII + O

= S + have/has + never + VpII + before

= S + haven't/hasn't + VpII + before

`1.` He hasn't gone abroad before.

`2.` I haven't tried sushi before.

`3.` They haven't visited the museum before.

`4.` This is the first time I have climbed this mountain.

`5.` This is the first time she has eaten a frog hotpot.

`6.` This is the first time I have been to Vietnam.

`------------------`

`***` QKĐ `⇔` HTHT (Áp dụng cho các câu):

`-` This/It is the first time + S + have/has + Vpp (Đây là lần đầu tiên ai đó làm gì)

`=` S + hasn't/haven't + Vpp + before (Ai đó chưa làm gì trước đó)

`=` S + has/have + never + Vpp (Ai đó chưa làm gì bao giờ)