Which substance plays a major role in almost all of the chemical reactions that occur in a living cell?

 Here's what I could find:

enzymes

The catalysts of biochemical reactions are enzymes and are responsible for bringing about almost all of the chemical reactions in living organisms.

Explanation: So sorry if this isn't what you need.

significant amounts of nitrogen oxides, carbon monoxide, and other pollution

explanation:

passenger vehicles are a major pollution contributor, producing significant amounts of nitrogen oxides, carbon monoxide, and other pollution. in 2013, transportation contributed more than half of the carbon monoxide and nitrogen oxides, and almost a quarter of the hydrocarbons emitted into our air.

yes i have all the correct answers

1. c 6. b. 11. c

2. a 7. d. 12. d

3. c 8. b. 13. c

4. d 9. c. 14. d

5. c 10. d. 15. a

16. d. 21. a

17. d.

18. a. 22-30 you must do on

19. d. your own

20. d.