Answer:
Ans. (C).Progesterone promotes fertility because its levels rise during ovulation and immediately after.
Progesterone is a female sex-hormone, produced in the ovaries right after ovulation and its level rise immediately after ovulation (as shown in graph). A thick, and proper uterine lining is important for the implantation of zygote in the uterine wall.
Progesterone has the most influence on a secure pregnancy as it promotes the thickening and maintenance of uterine lining. Low levels of progesterone makes it difficult to get pregnant as zygote cannot implant properly.