Which of the following statements about the lower respiratory system is incorrect?

• A. The tonsils in the pharynx help to keep pathogens from entering through food or air.
• B. The inside of the trachea is lined by the mucous membrane which can trap inhaled particles. 
• C. Bronchioles and alveoli are tightly encased in capillaries to facilitate gas exchange. 
• D. The pleural membrane around the lungs is a double-walled fluid-filled membrane. 

Answer: (C)

Verified step by step guidance

1. Step 1: Identify the anatomical structures mentioned in the statements and their locations within the respiratory system. The tonsils are part of the pharynx, which is in the upper respiratory tract, not the lower respiratory system.
2. Step 2: Understand the function of the mucous membrane lining the trachea. It traps inhaled particles, which is a protective mechanism of the lower respiratory tract.
3. Step 3: Analyze the statement about bronchioles and alveoli being tightly encased in capillaries. Recognize that this is a correct description of the lower respiratory system's structure to facilitate gas exchange.
4. Step 4: Review the description of the pleural membrane as a double-walled, fluid-filled membrane surrounding the lungs, which is accurate for the lower respiratory system.
5. Step 5: Determine which statement is incorrect by comparing each to the known anatomy and physiology of the lower respiratory system. Note that the tonsils are not part of the lower respiratory system, so the statement about them is incorrect in this context.