Across
- 2. used in incandescent light bulbs
- 4. used in red lighting in signs
- 5. gas released by grazing cattle, marshlands and rice fields
- 7. when the air becomes contaminated
- 8. needed by living organisms for respiration
- 9. gas used to inflate balloons and blimps
Down
- 1. place in the cell where respiration takes place
- 3. this term means the gas is unreactive
- 6. the most abundant gas in air