Which of the following is a mass within the ovary that secretes hormones to maintain the uterine lining during pregnancy?
A. Corpus luteum
B. Umbilical cord
C. Oocyte
D. Oviduct
Corpus luteum is responsible for secreting progesterone hormone that maintain the uterine wall, which is conducive for a fetus to develop.
Therefore, the Correct Answer is A.