SEP of 1 pt hmwk 3.2.1
The lead whose positive electrode is placed on the left leg is
O A. I
O B. aVR
O C. II
OD. aVL

The lead whose positive electrode is placed on the left leg is II or DII (option C).

Explanation:

The electrocardiogram or EKG is a method of recording the electrical activity of the heart, useful for the diagnosis of diseases related to rhythm and heart rate. The 12-lead EKG is commonly used.

The electrode located on the left leg corresponds to the positive pole of the II or D-II lead, a bipolar peripheral lead whose negative pole is on the right arm.  The electrode on the left leg is also the positive pole of the D-III lead, which goes to the left arm, and of the monopolar AVF lead.

The other options are not possible because: