Final answer:
About 70% to 80% of coronary arterial flow occurs during diastole, with option b (70%) being the closest correct answer from the choices provided.
Step-by-step explanation:
During the cardiac cycle, the majority of coronary arterial flow occurs during the diastolic phase when the heart muscle is relaxed. This relaxation allows the coronary arteries to fill with blood, supplying the heart muscle with oxygen and nutrients. The specific portion of the coronary arterial flow that occurs during diastole is about 70% to 80% of the total flow, making option b (70%) the closest answer from the choices provided. It's also pivotal to understand that the relaxation phase, or diastole, provides the essential perfusion of the heart's own muscular tissue, which is why a substantial portion of the coronary blood flow occurs during this phase.