Do scientists use the skeletal structure to classify organisms

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.

explanation:

b,bacteria convert nitrates

into nitrogen gas.

d,plants and animals take in

and use nitrogen compounds.

e,bacteria break down waste    

products and return nitrogen  

to the soil.

a,bacteria convert atmospheric

nitrogen to ammonia.

c,bacteria convert ammonia

to nitrites and nitrates.