Question

After several miles of running and sprinting in intervals, the runner’s muscles ache and feel fatigued. Which is the best explanation for what has occurred?
The runner's muscles have accumulated lactic acid.
The runner’s body has failed to perform cellular respiration.
The runner’s cells are relying completely on aerobic respiration.
The runner’s muscles have accumulated carbon dioxide.

Answer 1

old question but will answer so this can be closed. I'll go over the choices and explain why they're right/wrong

- The runner's muscles have accumulated lactic acid.

this is a true statement since intense exercise causes muscle cells to utilize fermentation because this process doesn't require oxygen (your body uses up a lot of oxygen during exercise so this alternative pathway is a way to produce ATP when oxygen supplies are limited)

we'll go over the others first just to be sure

- The runner’s body has failed to perform cellular respiration.

this is false, the body **is** still performing cellular respiration (fermentation is not enough to supply the body w/ atp)

- The runner’s cells are relying completely on aerobic respiration.

again, false, fermentation is an anaerobic process

- The runner’s muscles have accumulated carbon dioxide.
mostly false, co2 doesn't just accumulate in the body, it's removed/buffered to maintain pH and normal respiration