The answer to this question is C
Explanation:
because it allows you to eliminate or isolate variable/ it allows the experiment to minimize the changes in all the variables except the one being test.
I'm not gonna choose bc I'm not 100% sure either so read what's above, think it over and choose wisely
hope I helped a little and good luck :)
D. Daddy daddy said you were coming to my grandma to get some food now I need a bottle for you tomorrow and I’ll come bye lol I need a little girl e.
The answer is C because C represent plants and plants produce oxygen and absorb CO2