<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 35-year-old woman with irritable bowel syndrome comes to the physician because of increased diarrhea. She has not had any fever, bloody stools, nausea, or vomiting. The increase in stool frequency began when she started a new job. She is started on loperamide, and her symptoms improve. Which of the following is the primary mechanism of action of this drug?? A: μ-opioid receptor agonism, B: 5-HT3 receptor antagonism, C: Acetylcholine receptor antagonism, D: Physical protection of stomach mucosa, E: H2 receptor antagonismn,  <response>: This is a clinical vignette about a patient with irritable bowel syndrome and diarrhea who was started on loperamide. The question is asking about the primary mechanism of action of loperamide.Based on the clinical history provided, this patient likely has diarrhea-predominant IBS. Loperamide was started and improved her symptoms. Loperamide is an opioid receptor agonist that acts on μ-opioid receptors in the gut to decrease gut motility and secretion, therefore reducing diarrhea. The other options describe mechanisms of action of other types of medications used for GI conditions, but not the primary mechanism of loperamide.A: μ-opioid receptor agonism 