A 29 year old young man presents with complaints of recurrent attacks of diarrhea. He says his stools contain blood and mucous. Sometimes he has low grade fever. What is the most appropriate investigation for his condition?

The key is D. Barium enema. [Features are suggestive of IBD, so barium enema is the most relevant investigation among the given options. Barium contrast dye allows an evaluation of the intestines. This is more commonly used in severe IBD to rule out serious complications like a perforated colon].