Which of the following are the two phases of the ovarian cycle?

The correct answer identifies the two primary phases of the ovarian cycle as the follicular and luteal phases.

In the follicular phase, which begins on the first day of menstruation, the follicles in the ovaries mature. This phase ends with ovulation, when the ovary releases a mature egg. The hormone estrogen primarily drives processes during this phase, promoting the growth of the ovarian follicles and thickening the endometrial lining in preparation for a potential pregnancy.

Following ovulation, the cycle transitions into the luteal phase, characterized by the formation of the corpus luteum from the remnants of the ruptured follicle. This structure secretes progesterone, which is crucial for maintaining the endometrium and preparing it for implantation should fertilization occur.

Understanding these two phases is fundamental in grasping the broader concepts of the menstrual cycle, fertility, and hormonal regulation in reproduction. The other options contain phases that pertain to different aspects of the reproductive cycle or stages that do not specifically correspond to the ovarian cycle itself.