When the man first learns how to make a fire, he began to use fuel for the first time. The first fuel he used was probably wood. As time passed, the man eventually discovered that substances such as coal and oil (23)__________. Coal was not used very widely as a source of energy until the end of the 19th century. With the coming of the (24)__________ revolution, it was soon realized that production would double if coal was used instead of wood. Nowadays, many of the huge factories and (25)__________ generating stations would be unable to function if there was no coal. In the last forty or fifty years, however, the use of coal has declined. (26)__________ there have been changes in the coal industry. It is believed that more people would use coal if oil and gas were not (27)__________ available. There is more than enough coal in the world for man's needs for the next two hundred years if our use of coal does not increase. Unfortunately, however, about half of the world's coal would never be used. Mining much of it very expensive even if it was (28)__________ to use new equipment.
- A. are burning B. would burn C. have burn D. were burnt
- A. industrial B. national C. international D. worldwide
- A. resource B. panel C. innovation D. electricity
- A. Moreover B. As a result C. Because of D. In spite of
- A. believably B. readily C. efficiently D. willingly
- A. necessary B. important C. possible D. impossible
