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Lead III records the electrical difference between the right arm and the left leg. This lead is part of the traditional 12-lead electrocardiogram (ECG) system that utilizes limb leads to assess the heart's electrical activity. Specifically, in Lead III, electrodes are placed on the left leg and right arm, allowing for the measurement of the heart's electrical signals as they traverse through the body from the right arm to the left leg.

This configuration captures the downward and rightward electrical activity that reflects the overall depolarization pattern of the heart. Understanding the placement of these leads is critical, as each lead provides unique insights into the cardiac function and can help identify various cardiac conditions.

The other configurations do not correspond to Lead III; they might involve different combinations or placements of the limb leads but do not record the specific signals associated with Lead III. Hence, Lead III is distinctly characterized by the relationship between the right arm and the left leg.