On which day of the female's uterine (menstrual) cycle does ovulation typically occur?

Correct Answer: B

Rationale: The correct answer is B: Day 14. Ovulation typically occurs around day 14 of a female's menstrual cycle. This is because ovulation is triggered by a surge in luteinizing hormone (LH) which usually happens midway through the cycle. Ovulation marks the release of an egg from the ovary, making conception possible. Days 7, 21, and 24 are not typically associated with ovulation as they are either too early or too late in the menstrual cycle for the surge in LH to occur. It is important to note that the timing of ovulation can vary among individuals and cycles, but day 14 is considered the average for a 28-day menstrual cycle.

Correct Answer: A

Rationale: The correct answer is A. The hormone produced by the corpus luteum that helps maintain pregnancy is progesterone. After ovulation, the ruptured follicle forms the corpus luteum, which secretes progesterone to support the uterine lining for potential implantation. Choice B is incorrect as cleavage refers to early cell divisions in embryo development. Choice C is incorrect as fertilization is the fusion of sperm and egg. Choice D is incorrect as estrogen is primarily produced by the ovaries.

Correct Answer: A

Rationale: The correct answer is A because a spermatid is a mature male germ cell that arises from the process of spermatogenesis, not a secondary sex characteristic. - B is incorrect as a primary spermatocyte is indeed typical of males in the process of spermatogenesis. - C is incorrect as a secondary spermatocyte is an intermediate stage in spermatogenesis. - D is incorrect as deepening voice is a secondary sex characteristic associated with male puberty.

Correct Answer: D

Rationale: The correct answer is D: dilation stage. This is the stage of labor where the cervix dilates to allow for the passage of the baby through the birth canal. This stage is crucial for the progression of labor and eventual delivery of the infant. Option A, relaxin, is a hormone that helps soften the cervix and pelvic ligaments but is not directly related to the stage of labor mentioned. Option B, progesterone, is a hormone involved in maintaining pregnancy and preparing the uterus for implantation, not specifically related to the dilation stage. Option C, chorion, is a membrane surrounding the fetus and plays a role in nutrient exchange, not directly related to the dilation stage of labor.

Correct Answer: A

Rationale: After fertilization, the sperm and egg nuclei fuse to form a zygote. The egg completes its first meiotic division before fertilization, so A is incorrect. B is incorrect because the second polar body forms after fertilization. C is incorrect as the egg releases secretory vesicles to block polyspermy post-fertilization. D is incorrect as egg enzymes are activated post-fertilization to initiate embryogenesis. Thus, the answer is A, as the completion of the first meiotic division occurs before fertilization.