=>

1. I'd prefer not to chat online at the moment.

-> would not prefer to V ~ không muốn 

2. The victims haven't been provided with food and clothing yet.

-> bị động HTHT have/has (not) been V3/ed

3. Peter said that he would try to learn hard to pass the entrance exam.

-> câu tường thuật (will -> would)

4. If the soil weren't/wasn't badly polluted, trees and grasses would/could grow here.

-> câu đk loại 2: If S V2/ed, S would/could (not) V

5. All the workers of the plan were being instructed by the chief engineer.

-> bị động QKTD was/were being V3/ed

6. Quan said that he wanted to become a robot designer.

-> câu tường thuật (lùi thì, HTĐ -> QKĐ)

1. I prefer not to chat online 

2. The victims wasn't provided by them with food and clothing

3. Peter said that he would try to learn hard to pass the entrance exam

4. if the soil wasn't badly polluted, tress and grasses could grow here

5. all the workers of the plant were instructed bt the chief egineer

6. Quan said that he wanted to become a robot designer