During the cardiac cycle, heart sounds correlate with events of the cycle. Which is being associated with systole?

A. S2: This sound, also known as "dub," occurs during diastole when the semilunar valves close. B. S1: This sound, also known as "lub," occurs during systole when the atrioventricular valves close, marking the beginning of systole. C. S4: This sound is an abnormal heart sound associated with late diastole, not systole. D. S3: This sound is associated with early diastole and is typically related to rapid ventricular filling, not systole.