The parietal pleura represents a serous membrane that functions primarily in b) lining the thoracic cavity.
This membrane is one of the two layers of pleura surrounding the lungs. The other layer is called the visceral pleura, which directly covers the lungs. The parietal pleura adheres to the thoracic wall and the diaphragm, providing a smooth surface that allows the lungs to expand and contract easily during breathing.
While it might seem intuitive to think the parietal pleura could cover the lungs (a), it does not; instead, it forms a protective layer around the thoracic cavity, which houses the lungs and other mediastinal structures. It does not line the abdominal cavity (c) or cover the heart (d), therefore the correct answer is focused on its role in the thoracic cavity.