Question

if there is a sudden decline in the amount of _____, then menstruation occurs.
a follicle - stimulating hormone
b luteinizing hormone
c progesterone
d estrogen

Explanation:

Progesterone is crucial for maintaining the endometrium (the lining of the uterus). When progesterone levels decline (if fertilization does not occur), the endometrium breaks down, leading to menstruation. Follicle - stimulating hormone (FSH) is involved in follicle development, luteinizing hormone (LH) in ovulation, and estrogen in endometrial thickening (but progesterone's decline is the key trigger for menstruation among these options).

Answer:

C. Progesterone