The correct option is B pleura
Each lung is enclosed inside a double membraned structure called pleurae (singular- pleura). The outer membrane is called parietal pleura while the inner membrane is called visceral pleura. The narrow space between 2 pleurae is called pleural cavity which contains the pleural fluid.
The heart is covered by a double membrane bound structure called pericardium. The outer membrane is called parietal pericardium and the inner membrane is called visceral pericardium. The space between the 2 layers is called pericardial cavity and it contains the pericardial fluid.
Mediastinum is the partition between the two lungs but is usually defined as the interval between two pleural sacs.
Lungs are also called as pulmones.