Most of the Calcium That Triggers Contraction of Cardiac Muscle

Multiple Choice

Most of the calcium that triggers contraction of cardiac muscle comes

A) into the cell through leakage channels in the sarcolemma.
B) into the cell through voltage-gated channels in the sarcolemma.
C) from the sarcoplasmic reticulum of the cell.
D) from the Golgi apparatus of the cell.