One disadvantage of using photovoltaic cells to power a domestic water heater is that

A.     solar energy is a renewable source of energy.

B.     the power radiated by the Sun varies significantly depending on the weather.

C.     a large area of photovoltaic cells would be needed.

D.     photovoltaic cells contain CFCs, which contribute to the greenhouse effect.

C

To heat the amount of water used in a typical household, a large area of photovoltaic cells would be required and this is a disadvantage. Some candidates were distracted by the inclusion of the variation of weather conditions for one of the options, however candidates should have realized that the power radiated by the Sun is unaffected by the weather conditions on Earth.