• Fossil fuel
Fuels, such as gas, coal, and oil, that were formed underground from plant and animal remains millions of years ago.
• Turn upside down
To (cause something to) change completely.
The particular physical form or appearance of something.
Suitable for your purposes and needs and causing the least difficulty.
If someone or something is dependable, you can rely on him, her, or it.
To throw away or get rid of something because you no longer want it.
Source: BBC News