In acute respiratory distress syndrome,

Correct Answer: D

Rationale: ARDS lungs can be divided into infiltrated, consolidated, or collapsed areas (D), reflecting heterogeneous damage'. Choice A is false; abnormalities are not homogeneous some areas are spared, others severely affected. Choice B is incorrect; pneumonia often complicates fatal cases due to impaired clearance. Choice C is wrong; ARDS is typically unresponsive to O₂ therapy due to shunting (mortality ≈60%, not 20%). Choice E (60% mortality) is true but not listed. Page 716 notes ARDS's patchy nature ventilation-perfusion mismatch and fibrosis making D's regional division accurate, unlike A's uniformity or B's infection protection.

Correct Answer: B

Rationale: The most dangerous inhaled particles are 1-5 μm (B), reaching alveoli to cause fibrosis. Choice A is false; cases decline in the West due to regulation. Choice C is incorrect; larger particles (>10 μm) are filtered, causing less injury than 1-5 μm. Choice D is wrong; silica activates macrophages, releasing fibrogenic mediators (e.g., TNF), not inhibits. Choice E (not all exposed develop disease) is true. Page 733 confirms B's size range optimal for deep penetration and inflammation, unlike A's trend or D's mechanism.

Correct Answer: C

Rationale: Histologically, pulmonary alveolar proteinosis (PAP) shows acellular surfactant accumulation (C), not cellular exudate. Choice A is false; acquired PAP is most common. Choice B is true; acquired PAP is autoimmune (anti-GM-CSF). Choice D is incorrect; secondary PAP (e.g., silicosis) is rare. Choice E (congenital fatal) is true. Page 741 details C's morphology alveolar spaces fill with lipoproteinaceous material, contrasting with A's prevalence or D's frequency error.

Correct Answer: B

Rationale: Lobar pneumonia involves red to grey hepatization (B), marking RBC disintegration in consolidation. Choice A is false; Streptococcus pneumoniae is the most common cause. Choice C is incorrect; productive cough is typical. Choice D is wrong; atypical pneumonia, not lobar, links to immunosuppression. Choice E (age-specific) is a marker, not cause. Page 750 details B's sequence congestion to resolution via hepatization reflects S pneumoniae's progression, unlike A's rarity or C's cough denial.

Correct Answer: A

Rationale: Bronchogenic carcinoma often arises near the hilum (A), especially squamous cell. Choice B is false; metastasis is hematogenous and lymphatic. Choice C is incorrect; adrenals (>50%) outrank liver (30-50%). Choice D is wrong; adenocarcinoma/SCC (25-40%) exceed small cell (20-25%). Choice E (small cell resection poor) is true. Page 759 confirms A's origin hilar proximity reflects bronchial irritation, unlike B's spread or D's type error.