1. Social network has been used for many purposes by teenagers these days.

S + has/have+  been + V3/ed: bị động - thì HTHT 

2. I suggested that energy-saving appliances should be used instead of ordinary ones to save energy.

S + suggested + (that) + S + (should) + V1: đề nghị 

S +  should be + V3/ed: bị động 

3. If they were strong, they could lift the heavy door.

If 2: If + QKĐ, S + would / could + V1 

4. It was such an old table that we could keep it.

S + be +such + (a/an) + ADJ + N + that + clause: quá ... đến nỗi 

5. She invited me to have lunch with her.

S + invited + O + to V: mời 

6. A heavy shower prevented them from finishing their game of tennis.

prevent sb from sth: ngăn chặn ai làm gì 

7. They wanted to climb the mountain in spite of its danger.

In spite of / Despite + N / NP / Ving, clause: mặc dù 

tính từ sở hữu + N 

`color{orange}{~MiaMB~}`