The Primary Function of the Pericardial Sac Is to

The primary function of the pericardial sac is to

A) prevent excessive expansion of the heart as it fills with blood
B) secrete a fluid that reduces friction as the heart beats
C) serve as a reservoir for blood to be used during strenuous exercise
D) provide oxygen and nutrients to the heart muscle
E) catch and kill any bacteria in the blood flowing through the heart chambers