This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory, Subject name: Medicine
A 24-year old woman notices increasing shortness of breath after recent treatment for right lower lobe pneumonia. She has no fever, cough, or sputum production. On examination, the pertinent findings are decreased fremitus, dullness on percussion, and absent breath sounds of the right lower lung. In addition, the trachea has shifted to the left.For the above patient with abnormal pulmonary physical findings, select the most likely diagnosis. 
Select and explain. 
A. acute asthmatic attack, B. complete pneumothorax, C. large pleural effusion, D. atelectasis
C: large pleural effusion
Answer: C: large pleural effusion 
Explanation: Careful physical examination can be very useful in diagnosing many common pulmonary disorders. Atelectasis and large pleural effusions both can present with decreased fremitus, dullness or flatness to percussion, and absent breath sounds. In atelectasis, tracheal shift, if present, is toward the affected side, and the opposite for a large pleural effusion. Asthma's most typical manifestations are prolonged expiration and diffuse wheezing. However, impaired expansion, decreased fremitus, hyperresonance, and low diaphragms can also be found. A complete pneumothorax results in absent fremitus, hyperresonance or tympany, and absent breath sounds. Lobar pneumonia is characterized by consolidation with increased fremitus, dullness, and auscultatory findings of bronchial breathing, bronchophony, pectoriloquy, and crackles.