A 68-year-old male develops a fever of 101.5°F (38.6°C), tachypnea, and decreased breath sounds at the right lung base on post-operative day 2 following a laparoscopic cholecystectomy. What is the most likely initial diagnosis?

✓ Correct Answer: Option C

Atelectasis is very common post-operatively, especially on days 1-3, presenting with fever, tachypnea, and basal lung changes. It results from alveolar collapse due to hypoventilation and impaired cough, making it the most likely initial diagnosis.