The transmission of sound vibrations through the inner ear occurs chiefly through:

Correct Answer: D

Rationale: The correct answer is D: Liquid. Sound vibrations travel through the inner ear mainly through the liquid-filled cochlea. When sound waves reach the ear, they cause the fluid inside the cochlea to move, stimulating hair cells that convert the vibrations into electrical signals sent to the brain. Choice A (Bone) is incorrect as bone conduction bypasses the middle ear, while sound must pass through it to reach the cochlea. Choice B (Nerve fibers) is incorrect because nerves transmit the electrical signals generated by the hair cells, not sound vibrations themselves. Choice C (Air) is incorrect as the inner ear is filled with liquid, not air, and sound waves need a medium like air to travel through the ear canal but not inside the inner ear.

Correct Answer: C

Rationale: The correct answer is C: An inhibitor of progesterone’s actions. Progesterone is responsible for maintaining the uterine lining, and inhibiting its actions would prevent menstruation. Testosterone (A) and FSH (B) do not directly affect menstruation. Prostaglandin E2 (D) is involved in the menstrual process, but inhibiting it would not necessarily stop menstruation.

Correct Answer: D

Rationale: The correct answer is D because testosterone inhibits the hypothalamic secretion of gonadotropin-releasing hormone (GnRH) and the pituitary secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). This disruption in the normal hormonal feedback loop leads to the suppression of ovulation and the menstrual cycle. Option A is incorrect because inhibin is not directly affected by testosterone. Option B is incorrect as testosterone does not bind to endometrial receptors directly. Option C is incorrect because testosterone does not stimulate the secretion of FSH and LH from the anterior pituitary.

Correct Answer: D

Rationale: The correct answer is D: No corpus luteum is present. The corpus luteum is responsible for producing progesterone after ovulation. Without a corpus luteum, progesterone levels will be minimal, leading to a lack of menstrual cycles. A: If LH secretion rate is elevated, it would lead to increased corpus luteum formation and progesterone production. B: If LH secretion rate is suppressed, there would be insufficient stimulation for corpus luteum formation and progesterone production. C: FSH is responsible for follicle development, not progesterone production.

Correct Answer: A

Rationale: The correct answer is A. Birth control pills containing estrogen and progesterone prevent the preovulatory surge of luteinizing hormone (LH) secretion from the pituitary gland. This leads to the inhibition of ovulation, preventing the release of an egg from the ovary. Without ovulation, fertilization cannot occur, effectively preventing pregnancy. Choice B is incorrect because birth control pills do not prevent the development of ovarian follicles; they prevent ovulation. Choice C is incorrect because suppressing the function of the corpus luteum is not the primary mechanism of action of birth control pills. Choice D is incorrect because birth control pills do not prevent the normal development of the endometrium; they primarily prevent ovulation.