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: Social & Preventive Medicine
Pearl Index is expressed 
Select and explain. 
A. Per 10 woman years, B. Per 1000 woman years, C. Per 100 woman years, D. Per 50 woman years
C: Per 100 woman years
Answer: C: Per 100 woman years 
Explanation: None