The end of the vas deferens is a dilated sac called the _____.

Correct Answer: C

Rationale: The correct answer is C: ampulla. The ampulla is a dilated portion at the end of the vas deferens where it joins with the duct of the seminal vesicle to form the ejaculatory duct. This structure serves as a storage and mixing area for sperm and seminal fluid before ejaculation. The other choices, A: ductus deferens, is another name for the vas deferens itself; B: seminal vesicle is a gland that produces seminal fluid but is not the dilated sac at the end of the vas deferens; D: ejaculatory duct is formed by the union of the vas deferens and the duct of the seminal vesicle, it is not the dilated sac itself.

Correct Answer: A

Rationale: The correct answer is A: perimetrium. The perimetrium is the outer serosal layer of the uterus, providing protection and support. The other choices are incorrect: B. cervix is the lower portion of the uterus, C. endometrium is the inner lining where implantation occurs, and D. myometrium is the middle muscular layer of the uterus. The perimetrium is the outermost layer, making it the correct choice.

Correct Answer: B

Rationale: The correct answer is B: corpus luteum. Progesterone is primarily produced by the corpus luteum, which forms from the ruptured ovarian follicle after ovulation. The corpus luteum secretes progesterone to prepare the uterus for potential implantation of a fertilized egg. The Graafian follicle (choice A) is a mature ovarian follicle that contains the egg, but it does not produce progesterone. The secondary follicle (choice C) is an immature ovarian follicle and does not produce progesterone. The adrenal cortex (choice D) is responsible for producing other hormones like cortisol and aldosterone, not progesterone.

Correct Answer: B

Rationale: The correct answer is B: relaxin. The placenta produces estrogen, progesterone, and lactogen to support pregnancy. Relaxin is primarily produced by the corpus luteum and later by the placenta. However, it is not exclusively produced by the placenta, making it the correct choice. Estrogen is crucial for fetal development and maintaining pregnancy. Progesterone helps in preparing the uterus for implantation and supporting the pregnancy. Lactogen (human placental lactogen) plays a role in regulating maternal metabolism and fetal growth.

Correct Answer: A

Rationale: The correct answer is A: Basking shark. Ovoviviparous animals are those that produce eggs that hatch inside the mother's body, giving birth to live young. Basking sharks exhibit this reproductive strategy, making them ovoviviparous. Explanation of incorrect choices: B: Bonobos are primates and give birth to live young, but they are not ovoviviparous. C: Blue sharks give birth to live young as well, but they are not ovoviviparous. D: "None of the above" is incorrect as the basking shark is indeed an ovoviviparous animal, making it the correct answer.