**Core Concept**
Heart sounds are produced by mechanical events in the cardiac cycle. S2 marks the closure of the semilunar valves at the end of systole, and sounds occurring shortly after S2 are typically associated with valve closure, tissue movement, or pathology. Understanding the timing of these sounds is crucial for diagnosing valvular disease.

**Why the Correct Answer is Right**
Ejection click occurs during early systole, not shortly after S2. It is caused by the sudden stretching of the mitral valve leaflet during ventricular contraction, typically seen in mitral valve prolapse or mitral regurgitation. Since systole begins before S2, the ejection click happens *before* S2, not after. Therefore, it does not occur shortly after S2. All other sounds listed (opening snap, pericardial knock, tumor plop) are heard in late diastole or immediately after S2 due to valve closure or pericardial movement.

**Why Each Wrong Option is Incorrect**
Option A: Opening snap occurs just after S2 due to mitral valve opening in early diastole, marking mitral stenosis.
Option B: Pericardial knock is a sharp sound heard immediately after S2, due to pericardial tissue movement.
Option D: Tumor plop is a sound heard shortly after S2, associated with aortic valve stenosis or aortic regurgitation, due to sudden valve closure or tissue movement.

**Clinical Pearl / High-Yield Fact**
Remember: Sounds after S2 are related to diastolic events or valvular pathology. Ejection click is a systolic sound and occurs *before* S2 — a key point for differentiating systolic vs. diastolic valve sounds.

✓ Correct Answer: C. Ejection click