阅读理解。 Many, many years ago there were many forests on the earth. The trees died. They fell down, lay (躺) on the ground and became covered with earth. The trees of the old forests lay under the ground. The trees lay for thousands of years. After a long time the wood was changed. It became black and hard. It became coal (煤). Coal is not only used for burning. It is also used for many other things. For example, we can get beautiful colours from coal. The matters (物质) to colour the walls of rooms are got from coal. Coal is one of the most useful things in the world. 1. Many, many years ago, there were lots of _______ on the earth. [     ] A. wood B. trees C. coal D. stones 2. The trees fell down _______ they died. [     ] A. before B. after C. if D. or 3. The dead trees under the ground could be changed into _______. [     ] A. trees B. forests C. coal D. flowers 4. Coal is used for _______. [     ] A. burning B. many other things C. everything D. both A and B 5. _______ can be got from coal. [     ] A. Only colours B. Only one colour C. All things D. Many useful things