<span>I believe it is light, but this is kind of a confusing question. Technically there is a independent and dependent variable in the question. The variable being manipulated is light, and the earthwork activity depends on the light. </span>
Answer:
There needs to be enough sea urchins for otters to come and there needs to be enough otters to eat the urchins.
Explanation:
Mixture should be the answer.
Aerobic respiration happens in the mitochondrion of eukaryotic cells.
Anaerobic respiration does not use oxygen gas and happens in one process after glycolysis called Fermentation.
The process used to make beer would be a kind of fermentation, Alcohol fermentation, I believe.