What is geothermal energy?

Which process is used to harness nuclear energy these days? Explain it briefly.

List some advantages of solar cells.

The waste materials collected from a market complex are scrap paper,thermocol,vegetable waste,tin cans,and glass bottles. Which of these can be used for producing biogas? Mention three advantages of converting these into biogas rather than burning them.

Mention the advantages and limitations of wind energy.

Ram visited Manikaran Sahib in Himachal Pradesh where he saw an experimental geothermal plant. When he saw a hot spring,he wanted to know more about it. His father explained to him about geothermal energy and hot springs. Now answer the following questions:
$(a)$ What did Ram's father explain to him about hot springs?
$(b)$ Why is geothermal energy not generated on a large scale?
$(c)$ What is the main advantage of using geothermal energy?