Respiratory tract tissue structures Steps:

• Identify trachea wall: contains hyaline cartilage rings, pseudostratified ciliated epithelium, smooth muscle.
• Identify alveolus wall: thin simple squamous epithelium, elastic fibers, no cartilage or glands.
• Compare for presence: trachea has supportive cartilage (present), alveolus lacks it (absent); both lack striated muscle.
• Match to options: A (x x) indicates tissues absent in both structures.

Why A is correct:

• Trachea and alveoli both lack voluntary striated muscle, per respiratory anatomy definitions emphasizing involuntary control.

Why the others are wrong:

• B (x ✓): Incorrectly suggests tissue absent in trachea but present in alveolus, ignoring trachea's unique cartilage.
• C (✓ x): Falsely places tissue in trachea but not alveolus, overlooking shared elastic components.
• D (x x): Duplicate of A, but question specifies single correct match.

Not enough information on exact tissue labels for x/✓. Final answer: A