The _____________ regulates the flow of contents from the stomach to the duodenum.

The slow block is a mechanism that prevents polyspermy, which is the fertilization of an egg by more than one sperm. It does not prevent fertilization of another egg when one is already pregnant. The slow block involves changes in the egg's membrane after a sperm has entered, making it impermeable to other sperm. Therefore, this statement is false.

A. Corpus luteum; FSH and LH: The follicle transforms into the corpus luteum after ovulation, which secretes hormones. However, FSH and LH are hormones secreted by the pituitary gland, not products of the corpus luteum.

B. Corpus albicans; progesterone: The corpus albicans is a degenerated form of the corpus luteum and is not responsible for secreting progesterone.

C. Corpus albicans; estrogen and progesterone: The corpus albicans forms after the corpus luteum degenerates and does not produce significant levels of estrogen and progesterone.

D. Corpus luteum; estrogen and progesterone: After ovulation, the follicle transforms into the corpus luteum, which secretes estrogen and progesterone to support the early stages of pregnancy or regulate the menstrual cycle if pregnancy does not occur.