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
Which of the following is the earliest change in intestine which occurs in Crohn’s disease? 
Select and explain. 
A. Cobblestone appearance, B. Aphthous ulcer, C. Perforation, D. Stricture
B: Aphthous ulcer
Answer: B: Aphthous ulcer 
Explanation: Ref. Robbins Pathology. 9th edition. Page. 800
 
Crohns Disease

Present with skip lesions
Earliest lesion – Aphthous ulcers
Can involve whole of GIT – Form oral cavity to amus
Smoking is a risk factor
Fissure, fistula seen
Stricture seen
Gross features – Creeping pad of fat, Cobblestone appearance
Microscopy - Non caseating granuloma under microscopy, Transmural inflammation