The harnessing of which of the following leads to the destruction of large eco-systems?

The non-renewable source of energy among the following is :

Geothermal energy is produced by the:

Which of the following is not a consequence of establishing hydroelectric power plants ?

A certain form of energy is available due to the difference in the temperature of water at the surface of the ocean and its deeper levels.

(a) Name the form of energy.

(b) Is this energy ultimately derived from the sun or not?

(c) Explain how this form of energy can be converted into electricity.

(d) What is the minimum temperature difference in water at the surface of ocean and its deeper level which is required to operate power plants based on this energy ?