During a respiratory assessment, which of the following findings is most indicative of a pneumothorax?

Rationale: A. Stridor indicates upper airway obstruction, not a pneumothorax. B. Wheezing suggests narrowed airways, commonly seen in asthma or COPD, not pneumothorax. C. Absent breath sounds on one side are a hallmark finding of pneumothorax because air in the pleural space prevents lung expansion and sound transmission. D. Crackles are associated with fluid in the alveoli, such as in pneumonia or heart failure, not pneumothorax.