What causes a drop in female hormone levels? a: the onset of the menstrual flow. b: if an egg is released from the ovary. c: if the uterine wall thickens. d: if the egg is not fertilized.

Ans. (D). if the egg is not fertilized.

The major female sex hormones (estrogen and progesterone) are released by ovaries. During ovulation, ovary releases female gametes or eggs. After the release of eggs, corpus luteum is formed in the ovary, which releases both the female hormones (estrogen and progesterone) and prepare uterine lining for potential pregnancy.

When fertilization occurs, corpus luteum continuously secrets female hormones and allows implantation. However, if the egg is not fertilized, the corpus luteum starts to degenerate and secretion of female hormones stops.

Thus, the correct answer is option (D).

they float because they are less dense than the water itself

something denser than water, like a rock, will sink to the bottom

i'd say that the moon rock is about 2.2 billion years old.