As far as the sources of energy mentioned in the text ar...

The energy derived from coal, oil and gas is supposed to last for a long time.

Electricity which is generated by using the sun's energy is called solar power.

Electricity which is created by using the power of the wind is often called windmills.

River water in mountainous areas are not normally used to create hydroelectric power.

Electricity which is generated by water flowing in and out with the tides is enough to supply the world needs.