1
Relating to or derived from the sun
2
Movement of air caused by the uneven heating of the Earth's surface
3
Generating electricity by converting the energy of flowing water
4
Relating to or produced by the internal heat of the Earth
5
Organic matter used as a fuel, especially in a power station
6
Relating to or affected by tides
7
Capable of being replenished or replaced
8
Capable of being maintained at a steady level without exhausting natural resources
3
7
6
5
8
4
2
1