Answer the following question given this paragraph: 

The menstrual cycle is a series of changes in the reproductive system of mature females that repeats every month on average. It includes changes in the uterus as well as development of an egg and ovulation. If fertilization does not occur, menstruation occurs and the cycle repeats.


Q: What causes the menstrual cycle to be repeated?

 Choices:

- gravity

- uteris

- ovaries

- lack of fertilization

A:
lack of fertilization
