Pacemaker is situated in the

Options

A. wall of right atrium
B. interauricular septum
C. interventricular septum
D. wall of left atrium

Explanation

**Step-by-Step Solution:**

1. **Understanding the Pacemaker**: The pacemaker of the heart is known as the sinoatrial (SA) node. It is responsible for initiating the electrical impulses that regulate the heartbeat.

2. **Location of the Sinoatrial Node**: The sinoatrial node is specifically located in the upper wall of the right atrium of the heart.

3. **Conclusion**: Therefore, since the pacemaker is synonymous with the sinoatrial node, we can conclude that the pacemaker is situated in the upper wall of the right atrium.

4. **Final Answer**: The pacemaker is situated in the upper wall of the right atrium.

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