A. Incorrect. Chest X-rays are the initial step but may miss smaller volumes of air.
C. Incorrect. While useful, ultrasonography is typically used for confirming pneumothorax, not for detecting smaller volumes of air.
D. Incorrect. MRI is not typically used for diagnosing pneumothorax.
B. Correct! CT scans are more sensitive and can detect smaller volumes of intrapleural air and associated injuries.