Help me please I feel dead inside

First option

Explanatio

A

Explanation:

I would go with A. "Because.. blah etc".

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

the answer is lactic acid from anaerobic respiration. the acid in lactic acid is what creates sore and burning muscles. if you think about how acid burns that will give you a clue for questions like this.