The correct answer is (a) Solar cells.
Photovoltaic cells are a type of solar cell that converts light into electricity. They are made of semiconductor materials, such as silicon, that have a positive and negative charge. When light hits the cell, it creates an electric current that can be used to power devices.
Thermal cells are a type of cell that converts heat into electricity. They are made of materials that have a different electrical resistance when they are hot and cold. When heat is applied to the cell, it creates an electric current.
Sulphur cells are a type of cell that converts sulphur dioxide into electricity. They are made of a material that reacts with sulphur dioxide to produce an electric current.
Molar cells are a type of cell that converts molecules into electricity. They are made of a material that reacts with molecules to produce an electric current.
Photovoltaic cells are the most common type of solar cell. They are used in a variety of applications, including solar panels, calculators, and watches.