Choose the word or phrase among A, B, C, or D that best fits each blank space in the following passage.
About twenty per cent of the world’s present energy already comes from the sun in one form or another, special devices have already been made available to (21)......on the roofs of houses and flats to (22)......the sun’s rays and thus heat water. Thousands of these devices are now being used to provide 23).....in homes throughout the United States while more (24)......a million solar water-heating units have already been (25)......ill homes in Japan. Other purposes for.
which (26) .... energy is at present being used include the separation of salt from seawater, irrigation and sewage disposal.
(27).....most people in developing countries, the need is not for air conditioners or central heating but for cheap (28)...........of cooking food. drying crops, and lighting homes.
Number 26…..