What is the role of the corpus luteum during the menstrual cycle?

The correct answer is B: The corpus luteum produces progesterone to maintain the endometrium during the menstrual cycle. This hormone helps prepare the uterine lining for implantation in case fertilization occurs. Choice A is incorrect because estrogen is mainly produced by the developing follicles in the ovaries. Choice C is incorrect as testosterone is produced in smaller amounts by the ovaries and adrenal glands but does not play a significant role in maintaining the endometrium. Choice D is incorrect as the corpus luteum plays a crucial role in producing progesterone to support the endometrium.