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: Surgery
Malignant ulcer is differentiated from benign by 
Select and explain. 
A. Heaping up of margins, B. Fibrous scars radiating from crater, C. Induration of base, D. clean base
A: Heaping up of margins
Answer: A: Heaping up of margins 
Explanation: None