Why does solar cells have a great future?
(A) They provide a clean source of energy
(B) Supply of energy from sun is unlimited
(C) The cost of conventional sources of energy is rising while cells is reducing
(D) All of the above

Hint
We know that there are a lot of advantages to solar cells. It reduces environmental problems, it reduces health issues, it is eco-friendly and many more. Its demand is increasing day by day and many companies are working on it to enhance this device. We see that there are multiple options fitting here.

Complete step by step answer
Solar cell - it is a device which is used to convert light energy into electrical energy. Cells take this light energy from the sun that is why it got its name as solar cell; though it can take energy from artificial light also.
Phenomenon for this conversion are listed below:
- Light absorption
- Charge carriers get separated in opposite directions
- Transfer of those carriers to an external circuit.
It is a natural source of energy and therefore acts as a clean source. Source of energy is the Sun whose rays are unlimited and never ending. We don’t have to produce it which makes it free of cost I.e. eco-friendly whereas other products are very costly.
Since option (A), (B), (C) are correct. So, (D) all of the above is the correct solution.

Note
Source of energy is the sun which proves it to be a clean source of energy satisfying option (A). Since heat rays from the sun are never ending which satisfies option (B). We don’t have to pay to take this source of energy which satisfies option (C). This proves that option (A), (B), (C) are correct which is mentioned in option (D). Hence, (D) is the right solution.