This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Murmurs, Subject name: Medicine
The first hea sound is loud in which of the following conditions? 1. Mitral regurgitation 2. Pregnancy 3. Anemia 4. Mitral stenosis 
Select and explain. 
A. 1 and 4, B. 1, 2 and 4, C. 3 and 4, D. 2, 3 and 4
D: 2, 3 and 4
Answer: D: 2, 3 and 4 
Explanation: Loud S1-Tachycardia Sho PR interval CHF Anemia Pheochromocytoma Thyrotoxicosis Physiological: Children /pregnancy In Mitral stenosis-Physical obstruction- | Left atrial pressure S1 becomes softer in - Later stages of MS when the leaflets are rigid and calcified After exposure to beta adrenergic receptor blockers - Long PR intervals - left ventricular contractile dysfunction