In a normal human, The total lung capacity (TLC) is approximately equal to?

Correct Answer: A

Rationale: Total lung capacity (TLC) is the maximum air lungs hold after maximal inspiration, summing residual volume (RV, ~1-1.5 L), expiratory reserve volume (ERV, ~1-1.5 L), tidal volume (VT, ~0.5 L), and inspiratory reserve volume (IRV, ~2-3 L). In adults, TLC averages ~6 L (5-7 L, varying by sex, age, size), per standard physiology (e.g., Guyton). Two liters approximates FRC (~2.5-3 L), the resting volume. Four liters nears vital capacity (VC, ~4-5 L), excluding RV. Nine liters exceeds typical capacity, possibly hyperinflation. Six liters aligns with spirometry plus RV (e.g., helium dilution), reflecting full lung expansion in health, making it the best approximation for a normal human, widely validated across respiratory studies.

Correct Answer: D

Rationale: Per Poiseuille's law (R ∝ 1/r^4), a 10% airway diameter increase reduces resistance by ~40%, not increases it false. COPD (e.g., emphysema) is common due to smoking, not least false. Pulmonary fibrosis, restrictive, reduces compliance, not airway resistance (obstructive) false. In fibrosis, FEV1/FVC is ≥80% (normal or higher) as both FEV1 and FVC drop proportionally true, unlike obstructive diseases (<70%). This ratio's preservation reflects restricted volume, not airflow, a key diagnostic feature, making it the true statement amid misconceptions about resistance and prevalence.

Correct Answer: C

Rationale: Coastal regions have milder climates due to water's high specific heat capacity (~4.18 J/g°C) and greater evaporation, moderating temperatures. Evaporation and cloud cover increase humidity, reflecting solar radiation and stabilizing heat summers cool, winters warm compared to inland. Water's albedo (~0.06) is low, absorbing more heat, not reflecting it false. Water's specific heat is higher, not lower, than land (~1 J/g°C), storing energy false. Latitude affects insolation broadly, not coast-specific false. Evaporation and clouds, tied to water's thermal inertia, buffer temperature swings, a key maritime effect (e.g., Mediterranean climates), making this the best explanation.

Correct Answer: B

Rationale: A bronchopulmonary segment is a functional lung unit supplied by a segmental (tertiary) bronchus (A), segmental pulmonary artery (E, implied), nerves (C), and lymphatics (D), all within its connective tissue boundaries. The segmental bronchus delivers air, the artery supplies blood, and nerves and lymphatics manage innervation and drainage. However, pulmonary veins (B) are not segment-specific; they run intersegmentally, collecting blood from multiple segments into larger lobar veins, not confined within a single segment's borders. This venous drainage pattern ensures efficient oxygenation return but excludes B from being a defining component of the segment's structure, unlike the artery and bronchus, which are segmentally discrete. Thus, B is the exception.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.