Final answer:
Coronary artery blood flow peaks during diastole to supply the heart muscle with oxygen and nutrients, which is essential for its function and not related to preventing blood clots, aiding digestion, or cooling down the heart.
Step-by-step explanation:
Coronary artery blood flow peaks when the heart relaxes, during the phase known as diastole. During this relaxation phase of the cardiac cycle, the ventricles are filled with blood. The peak blood flow is crucial because it supplies the heart muscle with oxygen and nutrients, which is essential for the heart's function. If the heart cannot get enough oxygen, conditions such as angina or myocardial infarction (heart attack) can occur.
To prevent blood clots is not a direct reason for peak coronary artery flow during diastole, although good blood flow can minimize the risk of clot formation. To aid digestion is not related to coronary artery blood flow, and to cool down the heart is also not a purpose of increased blood flow during diastole.
The correct reason for why coronary artery blood flow peaks when the heart relaxes is c) To supply oxygen to the heart muscle.