This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
Below X-ray is seen in: 
Select and explain. 
A. Ulcerative colitis, B. Carcinoma colon, C. Crohn's disease, D. Whipple's disease
A: Ulcerative colitis
Answer: A: Ulcerative colitis 
Explanation: Pipestem colon is seen in ulcerative colitis
String sign of Kantor is seen in Crohn 's disease.