Câu hỏi:

When man first learned how to make a fire, he began to use fuel for the first time. The first fuel he used was probably wood. As time (1) man eventually discovered that substances such as coal and oil (2). Coal (3) very widely as a source of energy until the last century. With the coming of the industrial revolution, it was soon realised that production (4) if coal was used instead of wood. Nowadays, many of the huge factories and electricity generating stations (5) to function if there was no coal. In the last twenty or thirty years, however, the use of coal (6). As a result, there have been changes in the coal industry. It (7) that more people (8) coal if oil and gas were not so readily 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 (9). Unfortunately, however, about half of the world's coal (10). Mining much of it would be very expensive even if it was possible to use new equipment.

1. A - passes              B - used to pass                    C - would pass          D - passed

2. A - are burning    B - would burn                     C - have burnt           D - were burnt

3. A - not used         B - did not use                      C - not using              D - was not used

4. A - doubles          B - had double                      C - will double          D - would double

5. A - were unable   B - would be unable             C - will be unable     D - are unable

6. A - has declined  B - will decline                     C - declines               D - would decline

7. A - believed         B - is believing                     C - believing             D - is believed

8. A - would use      B - used                                 C - use                        D - will use

9. A - did not increase                                             B - would not increase

    C - does not increase                                           D - may not increase

10. A - would never use                                          B - may never be used

      C - would never be used                                   D - may never use