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: Gynaecology & Obstetrics
Mean incubation period for primary syphilitic chancre is 
Select and explain. 
A. 1 week, B. 2 weeks, C. 3 weeks, D. 4 weeks
C: 3 weeks
Answer: C: 3 weeks 
Explanation: Mean incubation period is 3 weeks.