Question

the first part of the cardiac cycle is called
a atrial repolarization
b ventricular repolarization
c atrial depolarization
d ventricular depolarization

Explanation:

The cardiac cycle begins with atrial depolarization. This is when the atria (upper chambers of the heart) contract to push blood into the ventricles. Atrial repolarization occurs after depolarization. Ventricular depolarization happens after atrial depolarization (it's the next step in the cardiac cycle where ventricles contract). Ventricular repolarization is later in the cycle.

Answer:

C. atrial depolarization