Final answer:
The visceral pericardium and the epicardium refer to the same layer of tissue around the heart, called the epicardium as part of the heart wall and the visceral pericardium as part of the pericardium.
Step-by-step explanation:
The terms visceral pericardium and epicardium are essentially referring to the same layer of the heart's wall, but with a difference in perspective related to their functions and anatomical position. When we describe the visceral pericardium, we are referring to it as part of the serous pericardium that is the inner layer coming into direct contact with the heart. This layer is also known as the epicardium when considering it as the outermost layer of the heart wall itself. In essence, the epicardium is part of the visceral pericardium, meaning that choices a and d from the provided options are both correct as they describe a relationship where both terms represent the same anatomical structure seen in two different contexts: the outer layer of the heart and the inner layer of the pericardium.