Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word that best fits each of the numbered blanks. In the modern world, people depend on energy to power their everyday lives. A wide range of power-run devices and modern conveniences (23) ________, and although it may seem that we will not be in danger of living without those conveniences, the fact is that many supplies of energy are running our rapidly. Scientists are constantly (24) ______ new sources of energy to keep modern society running. Whether future populations will continue to enjoy the benefits of abundant energy will depend (25) ________ the success of this search. Coal, oil, and natural gas are now being used widely. (26) _______, these supplies are limited, and they are a major source of pollution. Therefore, the existing alternative energy sources must be improved or further explored and developed. These include nuclear, water, solar, and wind power, as well as energy from new, (27) ______ types of fuels. Each of these, however, has advantages and disadvantages. 23. A. are used B. used to C. are using D. use 24. A. looking for B. searching for C. researching D. finding 25. A. On B. for C. with D. in 26. A. Moreover B. Because C. Although D. However 27. A. Polluting B. polluted C. nonpolluting D. pollution