Which condition is characterized by the sudden onset of shortness of breath, often occurring at night and associated with heart failure?
Correct Answer: A
Rationale: The correct answer is A: Paroxysmal nocturnal dyspnea. This condition is characterized by sudden onset of shortness of breath at night, often associated with heart failure. It occurs when a person lies down due to fluid redistribution in the body, leading to increased pressure on the lungs and heart. Sleep apnea (B) is a separate condition characterized by pauses in breathing during sleep. Orthopnea (C) is difficulty breathing while lying flat, relieved by sitting up. Dyspnea (D) is a general term for shortness of breath but does not specifically refer to the sudden onset at night associated with heart failure.