This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T, Subject name: Surgery
In classic Barret's, the length of columnar epithelium in distal oesophagus is 
Select and explain. 
A. >1cm, B. >2cm, C. >3cm, D. >4cm
C: >3cm
Answer: C: >3cm 
Explanation: Classic Barrett's (>= 3cm columnar epithelium);Sho-segment Barrett's (<3 cm of columnar epithelium);Cardia metaplasia (intestinal metaplasia at the oesophagogastric junction without any macroscopic change at endoscopy).The relative risk of cancer rises with increasing length of abnormal mucosa.