It is important to note, however, that ECGs record the electrical currents generated by cardiac muscle indirectly : They measure the electrical activity present in body fluids from the cardiac impulse that reaches the body surface. What other aspect of this method should one remember when analyzing ECGs

It is important to note, however, that ECGs record the electrical currents generated by cardiac muscle indirectly. They measure the electrical activity present in body fluids from the cardiac impulse that reaches the body surface. What other aspect of this method should one remember when analyzing ECGs?
a. Leads can detect separate potentials from ventricular depolarization and atrial repolarization.
b. Orientation of the electrodes on the body surface can affect the output in an ECG.
c. It follows the activity of a single action potential in a single cell at a single point in time.

Ithink the answer is d.