This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Family Planning, Subject name: Social & Preventive Medicine
[{'content': 'Pearl index is defined as? \nSelect and explain. \nA. Accidental pregnancies per 1000 women-years of exposure, B. Accidental pregnancies per 100 women-years of exposure, C. Accidental pregnancies per 10 women-years of exposure, D. Accidental pregnancies per women-years of exposure', 'role': 'user'}, {'content': 'Answer: B \nExplanation: ANSWER: (B) Accidental pregnancies per 100 women-years of exposureREF: Parks 22 Ed page 471, Dutta 6th ed p. 532Repeat Post Diploma June 2012, December 2011, June 2009 SeeFootnote of APPENDIX-115 METHODS OF CONTRACEPTION', 'role': 'assistant'}]