The heart sound "DUP" is Produced when `:-`

Options

A. Mitral valve opens
B. Mitral valve closes
C. Semilunar valve at the base of aorta closes
D. Tricuspid valve opens

Answer

### Step-by-Step Solution:

1. **Understanding Heart Sounds**: The heart produces two main sounds during its cycle, commonly referred to as "lub" and "dup". These sounds are associated with the closing of heart valves.

2. **Identifying the Sounds**:
- The first sound, "lub" (S1), is produced primarily by the closure of the atrioventricular (AV) valves, which include the mitral and tricuspid valves.
- The second sound, "dup" (S2), is produced by the closure of the semilunar valves.

3. **Focus on the "Dup" Sound**: The "dup" sound specifically corresponds to the closure of the semilunar valves, which are located at the base of the aorta and the pulmonary artery.

4. **Mechanism of Sound Production**:
- During the cardiac cycle, when the ventricles finish contracting and begin to relax, the pressure in the ventricles falls below the pressure in the aorta and pulmonary artery.
- This pressure difference causes the semilunar valves (aortic and pulmonary valves) to close, leading to the production of the "dup" sound.

5. **Sequence of Closure**:
- The aortic valve closes slightly before the pulmonary valve due to the higher pressure in the aorta (approximately 80 mm Hg) compared to the pulmonary artery (approximately 10 mm Hg).
- This difference in pressure results in the aortic valve closing first, followed by the pulmonary valve, contributing to the distinct sound of "dup".

6. **Conclusion**: Therefore, the heart sound "dup" is produced when the semilunar valves at the base of the aorta close.

### Final Answer:
The heart sound "DUP" is produced when the semilunar valve at the base of the aorta closes.

---