`3`. If we allow people to hunt endangered species, they will become extinct soon.

`-` Câu điều kiện loại `1`: If + S + V(-s/es), S + will + V-inf

`4`. I haven't called her since she left me.

`-` S + have/has + not + VpII + since + S + V-ed/c2

`5`. Quang can swim better than Minh.

`-` So sánh hơn: S + V + adv-er/more adv + than + S2

`6`. Even though it rained, a lot of people came to the concert.

`-` Even though + S + V, S + V: Mặc dù

1. Her classmates weren't invited to the party.

S + was/were + (not) + V3/ed (bị động - thì QKĐ)

2. Đúng

3. If they allow people to hunt endangered species, they will become extinct soon.

if loại 1: If + S + V1/s/es, S + will/can/shall + V1 

4. I haven't called her since she left me.

S + has/have + not + V3/ed + for/since + time 

--> S + last + V2/ed 

--> The last time + S+ V2/ed + was + time 

--> It is / has been + time + since + S+ (last) + V2/ed 

5. Quang can swim better than Minh.

S + be/ V+  better than + O : so sánh hơn

6. Even though it rained, a lot of people came to the concert.

Even though + clause, clause: mặc dù

`color{orange}{~LeAiFuRuiHuiBao~}`