Read the followingpassage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks

Solar energy is a long lasting source of energy, and it can (21)________almost anywhere.To generate solar energy, we only need solar cells and (22)________! Solar cells can easily be installed on house (23)________, so we don’t need any new space.Compared to other renewable sources, they also possess many advantages:wind and water power rely on turbines which (24)________noisy, expensive and which take up large space.Solar cells are totally silent and (25)________.As they have no moving parts, they require little maintenance and have a long lifetime.

A. be used

B. is used

C. be using 

D. to be used