**Core Concept**
Mitral stenosis is a valvular heart disease characterized by the narrowing of the mitral valve opening, impeding blood flow from the left atrium to the left ventricle. This condition often results from rheumatic fever and can lead to significant morbidity if left untreated.

**Why the Correct Answer is Right**
The correct answer is based on the classic clinical presentation of severe mitral stenosis, characterized by symptoms of left atrial hypertension and subsequent pulmonary congestion. This typically manifests as orthopnea, paroxysmal nocturnal dyspnea, and a prominent S3 heart sound due to increased left atrial pressure. The increased pressure in the left atrium also leads to pulmonary edema and a characteristic "opening snap" followed by a mid-diastolic murmur.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect as it does not accurately describe the typical presentation of severe mitral stenosis.

**Option B:** This is incorrect as it is more characteristic of severe mitral regurgitation, not stenosis.

**Option C:** This is incorrect as it is more characteristic of aortic stenosis, not mitral stenosis.

**Clinical Pearl / High-Yield Fact**
The presence of a prominent S3 heart sound in a patient with mitral stenosis is a critical clinical finding, as it suggests increased left atrial pressure and the need for urgent intervention.

**Correct Answer: B. Severe mitral stenosis is characterized by orthopnea, paroxysmal nocturnal dyspnea, and a prominent S3 heart sound due to increased left atrial pressure.**