Final answer:
The correct option that includes structures solely enclosed within the mediastinum is 'C) esophagus, trachea, thymus'. Lungs are positioned in the pleural cavities and not within the mediastinum.
Step-by-step explanation:
The structures enclosed within the mediastinum include the heart, esophagus, trachea, thymus, and major vessels among others but not the lungs. When we look at the choices provided, the correct option that includes ONLY structures within the mediastinum is option 'C) esophagus, trachea, thymus'. The lungs are not enclosed within the mediastinum; instead, they are situated in the pleural cavities on either side of the mediastinum.
The esophagus is a muscular tube through which food passes from the pharynx to the stomach. It passes through the esophageal hiatus of the diaphragm. The trachea is part of the respiratory system through which air moves from the larynx to the bronchi. Lastly, the thymus is a specialized organ of the immune system, located in the superior mediastinum, above the heart.