Answer:
C. All muscle contractions after Sarah reaches fatigue (about an hour into her run)
Explanation:
At the start of the marathon race, the main source of Sarah's energy will be the Adenosine Triphosphate (ATP) that her muscle has stored. After the exhaustion of the ATP stored, which averagely will be about an hour into the race, the creatine phosphate (which will be converted to ATP) will be her major energy source. But due to the non functionality of the creatine phosphate that she produces, there will be muscle contractions which will affect her race. Therefore, Sarah will suffer muscle contractions after she reaches fatigue( about an hour into her run)