Final answer:
The pericardial cavity exclusively contains the heart, which is protected and lubricated by serous fluid within the compartment.
Step-by-step explanation:
The pericardial cavity contains the heart. The ventral body cavity, in which the pericardial cavity resides, is subdivided into the thoracic and abdominopelvic cavities. The thoracic cavity consists of the pleural cavities, each surrounding a lung, and the pericardial cavity, which contains the heart and is situated within the mediastinum. The abdominopelvic cavity, on the other hand, is further separated into the abdominal cavity, housing digestive organs and kidneys, and the pelvic cavity, which contains reproductive organs and organs of excretion.
Therefore, the correct answer to which organ the pericardial cavity contains is A) heart, as it serves as a protective compartment for the heart, reducing friction through a serous fluid that lubricates the heart during its pumping action.