The correct option is A 28 days
The reproductive cycle in female primates is called menstrual cycle.
The average duration of a menstrual cycle is about 28 days. The
duration of menstrual cycle varies in different females as it is dependent upon a number of factors. In some women, the cycle lasts upto 35 days.
The various phases of menstrual cycle include: menstrual or bleeding phase, follicular phase, proliferative phase, ovulatory phase and luteal phase.