This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
Which of the following is not seen in ARDS 
Select and explain. 
A. Pulmonary edema, B. Hypoxemia, C. Stiff lung, D. Hypercapnia
D: Hypercapnia
Answer: D: Hypercapnia 
Explanation: Acute respiratory distress syndrome is a clinical syndrome of severe dyspnoea of rapid onset,hypoxaemia,and diffuse pulmonary infiltrates leading to respiratory failure.It is also known as hyaline membrane disease.The exudative phase is characterised by alveolar/pulmonary edema predominantely involving dependent poions of the lung,leading to diminished aeration,hypoxaemia,& atelectasis.As a result ofncoating of the alveoli with hyaline membranes,there is loss of surfactant causing collapse called 'stiff lung'. ARDS is characterized by type 1 respiratory failure which has only hypoxia but the value of CO2 is normal. ARDS has noncardiogenic pulmonary edema with normal PCWP. Reference:Harrison's medicine-18th edition,page no:2205-2207,Textbook of pathology-Harsh Mohan,6th edition,page no:463