Which lead is formed between the right arm and left leg electrodes?

• A. Lead II
• B. Lead I
• C. Lead III
• D. aVL

Answer: (A)

The key idea is that limb leads are created by measuring the electrical potential difference between two limbs. The pair of electrodes on the right arm and the left leg forms a lead whose negative electrode is on the right arm and whose positive electrode is on the left leg, producing a vector that points from the right arm toward the left leg. That specific arrangement corresponds to Lead II. The other standard limb leads pair different limbs: right arm–left arm for Lead I, and left arm–left leg for Lead III. The augmented left-arm lead (aVL) is a unipolar lead with its positive electrode on the left arm and uses a composite reference from the other limbs, not a direct RA-to-LL pair. So the lead formed between the right arm and left leg electrodes is Lead II.