1. Solar power is one of the cheapest and cleanest effective sources of energy. (so sánh nhất tính từ ngắn: S + tobe + the + adj_est)

2. It is provided freely by the sun. (bị động thì HTĐ)

3. Solar energy will be used by many countries in the world. (Bị động thì TLĐ)

4. People install solar panels on the roof of houses. (HTĐ)

5. This time tomorrow they will be studying at the library. (TLTD, dấu hiệu: this time tomorrow)

6. Solar energy will be used by many countries in the world. (Bị động thì TLĐ)

7. I think biogas is abundant and cheap for cooking heating. (HTĐ)

8. Is wind a renewable source of energy? (HTĐ)

9. We reduce using electricity to save energy. (HTĐ)

10. By using solar energy, the problem of the energy shortage is solved. (bị động thì HTĐ)