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: Pathology
Characteristic feature of amoebic ulcer -a)  Flask shapedb)  Undermined edgesc)  Rolled up edged)  Punched out 
Select and explain. 
A. ac, B. a, C. ad, D. ab
D: ab
Answer: D: ab 
Explanation: Amebiasis most frequently involves the cecum and ascending colon, followed in order by the sigmoid, rectum and appendix.
The ulcerative lesions develop undermining of margins of the ulcer due to lytic action of the trophozoites.
Ulcer has a flask shaped with a narrow neck and broad base.