As the Heart Beats, Friction Between the Pericardial Membranes Is

Question

As the heart beats, friction between the pericardial membranes is prevented by:
A)serous fluid
B)plasma
C)mucus
D)endocardial fluid

Accepted Answer

Serous fluid is a lubricating fluid that is secreted by the serous membrane, which is one of the pericardial membranes. This fluid helps to reduce friction between the membranes during the beating of the heart.