1. I haven't seen Nam for 3 years.

-> It's + khoảng thời gian + since + S2 + last + V2/ed = S + have/has + Vpp + for 

2. Carol told Peter not to make so much noise.

-> tell + SO + to V/ not to V: yêu cầu ai đó làm gì/ không làm gì 

3. It's very important to keep the environment clean.

-> It's be + adj + to V

4. Mrs Hoa suggested that Nam should turn off all the lights before going out.

-> suggest + that + S + should + Vinf

5. How about planting some trees around your house to get fresh air ?

-> how about + Ving 

1. I haven't saw Nam for 3 years

2. Carol told Peter doesn't make so much noise

3. It's is important to keep the environmet clean

4. Mrs Hoa suggested turn off the light before going out

5. How about planting some tree around ypur house + ghi hết phần còn lại (V1)

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