1. They intend to make this beach a clean and beautiful place again.

-> They plan to make this beach a clean and beautiful place again. (intend to V= plan to V: lên kế hoạch làm gì)

2. The students started to collect old clothes for their charity programme last week.

-> The students have collected old clothes for their charity programme since last week.  (Những học sinh đã thu thập quần áo cũ cho chương trình từ thiện từ tuần trước) 

3. If I don't leave now, I'll miss my train.

-> Unless I leave now,I'll miss my train. (Unless = if not: nếu không)

4. Students at our school do a lot of outdoor activities.

-> Students at our school take part in a lot of outdoor activities. (take part in: tham gia) 

5. Phuc is the most intelligent student in the class.

-> No student in the class is more intelligent than Phuc. (không ai trong lớp thông minh hơn Phúc) 
Có gì không hiểu bạn hỏi mình bên dưới nha 
Chúc bạn học tốt!!
Hy vọng bạn cho mình 5 sao và trả lời hay nhất nha 

1. They intend to make this beach a clean and beautiful place again.

-> They plan to make this beach a clean and beautiful place again.

           ( plan + to V : lên kế hoạch/ dự định làm gì )

2. The students started collecting old clothes for their charity programme last week. (sửa lại to collect thành collecting)

-> The students have collected old clothes for their charity programme for one week.

          ( S + have/has + PII + for + khoảng thời gian)

3. If I don't leave now, I'll miss my train.

-> Unless I leave now, I'll miss my train.

          If S + don't/ doesn't + V, S + will + V

         = Unless S + V, S + will + V

4. Students at our school do a lot of outdoor activities.

-> Students at our school take part in a lot of outdoor activities.

        ( take part in : tham gia/ thực hiện hoạt động gì đó)

5. Phuc is the most intelligent student in the class.

-> No student in the class is more intelligent than Phuc.

       No one + (in + nhóm) + (be) + adj/adv + than + S