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
Common presenting symptom of pneumocystis carini pneumonia Is 
Select and explain. 
A. Cavity on X-ray, B. Haemoptysis, C. Breathlessness, D. Purulent sputum
C: Breathlessness
Answer: C: Breathlessness 
Explanation: The key presenting symptom of PCP is progressive dyspnoea.Dry cough & fever are common.Physical findings include tachypnoea,tachycardia,and cyanosis.Chest X ray shows typical 'ground-glass' interstitial infiltrates in the perihilar regions.Pneumatoceles may occur and rupture,resulting in a pneumothorax. Reference: Davidson edition23rd pg 585