Devansh -for you

1. Which is the second  most plentiful gas in the air?
2. How do the living beings take  oxygen?
3. How do green plants produce oxygen?
4. How does the oxygen content remain constant in the air?
5. Why must we not destroy the trees?
6. Why is carbon-di -oxide an important gas?
7. Who releases this gas?
8. How  a perfect balance is obtained?
9. What  makes this balance upset?
10. What adds billions of tons of this gas?
11. What happens because of this imbalance?