Final answer:
The correct answer is B. The visceral layer of the serous pericardium is also known as the epicardium, which is a macroscopic layer on the heart's surface that secretes fluid to reduce friction.
Step-by-step explanation:
The term epicardium is used to describe the visceral layer of the serous pericardium that lines the surface of the heart. In most organs, visceral serous membranes, including the epicardium, are microscopic. However, in the heart, it is a macroscopic layer composed of mesothelium and connective tissue.
The mesothelium secretes serous fluid into the pericardial cavity, reducing friction as the heart contracts. The pericardium, which encapsulates the heart, consists of two main layers: the serous pericardium and the more robust fibrous pericardium. The serous pericardium itself is split into two layers, with the epicardium being the inner layer that is in direct contact with the heart muscle (myocardium).