<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 29-year-old man presents to the clinic with several days of flatulence and greasy, foul-smelling diarrhea. He says that he was on a camping trip last week after which his symptoms started. When asked further about his camping activities, he reports collecting water from a stream but did not boil or chemically treat the water. The patient also reports nausea, weight loss, and abdominal cramps followed by sudden diarrhea. He denies tenesmus, urgency, and bloody diarrhea. His temperature is 37C 98.6 F, respiratory rate is 15min, pulse is 107min, and blood pressure is 8958 mm Hg. A physical examination is performed where nothing significant was found except for dry mucous membranes. Intravenous fluids are started and a stool sample is sent to the lab, which reveals motile protozoa on microscopy, negative for any ova, no blood cells, and pus cells. What is the most likely diagnosis?? A: Giardiasis, B: C. difficile colitis, C: Irritable bowel syndrome, D: Travelers diarrhea due to Norovirus, E: Travelers diarrhea due to ETEC,  <response>: Based on the information provided in the question stem, the key findings are:- 29-year-old man with flatulence, greasy foul-smelling diarrhea, nausea, weight loss, and abdominal cramps after a recent camping trip- He drank untreated stream water while camping - Vital signs show tachycardia and hypotension indicating dehydration- Physical exam unremarkable except for dry mucous membranes sign of dehydration- Stool sample showed motile protozoa, no blood or pus cells- The onset of symptoms after drinking untreated stream water while camping along with the presence of protozoa in the stool make giardiasis the most likely diagnosis. The other choices can be ruled out: - C. difficile colitis causes bloody diarrhea and is associated with antibiotic use which is not mentioned. - Irritable bowel syndrome is a chronic condition not caused by an infection.- Norovirus and ETEC diarrhea are acute self-limited illnesses, not consistent with the chronic symptoms lasting weeks described here.A: Giardiasis 