This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Spirochetes, Subject name: Microbiology
Characteristic of primary chancre:(1988) 
Select and explain. 
A. Painless punched out ulcer, B. Painless ulcer with over hanging edges, C. Painless ulcer with irregular raised edges, D. Painful punched out ulcer
A: Painless punched out ulcer
Answer: A: Painless punched out ulcer 
Explanation: Ans: a (Painless punched out ulcer)Ref: Ananthanarayan Micro, 7th ed, p. 379 & 6th ed, p. 350, Harrison, 16thed, p. 979 & 15th ed, p. 1048