Across
- 3. Natural gas mainly contains ______.
- 6. _____is responsible for global warming.
- 8. ________ is a mixture of hydrogen, methane, carbon monoxide and other gases.
- 9. _________ is used for surfacing of roads.
Down
- 1. _______ contains 90% of carbon.
- 2. _______ is used to prepare coke and coal tar.
- 4. Composition of petroleum.
- 5. _______ is known as brown coal.
- 7. Components obtained by refining of petroleum.