Fertile period in a women with menstural cycle of 26-31 days -

Ans. is 'a' i.e., 8-21 days of cycle Safe Period (rhythm method)o This is also known as the calendar method first described by Ogino.o The method is based upon the fact that ovulation occurs from 12 to 16 days before the onset of mensturation.o Calculation is as follows:The shortest cycle minus 18 days gives the first day of the fertile periodThe longest cycle minus 10 days gives the last day of fertile period.For example, if a woman's mensturai cycle varies from 26-31 days, the fertile period during which she should not have intercourse would be from the 8th day to 21st day of the mensturai cycle, counting day one as the first day of the mensturai period.