The tiny ball of 16 cells found freely

Correct Answer: C

Rationale: The correct answer is C: blastocyst. At this stage of development, the embryo is a hollow ball of cells with an inner cell mass. This structure is called a blastocyst. A is incorrect because testosterone is a hormone, not a cell structure. B is incorrect as it does not describe the early stage of embryonic development. D is incorrect as luteinizing hormone is a hormone involved in the menstrual cycle, not embryonic development.

Correct Answer: C

Rationale: The correct answer is C: 400,000,000. During ejaculation, a healthy male typically releases around 200-500 million sperm cells. Choice A (4,000) and B (40,000) are too low compared to the average sperm count. Choice D (4,000,000) is also significantly lower than the typical sperm count, making it incorrect. Therefore, C is the correct answer as it aligns with the standard range of sperm count during ejaculation.

Correct Answer: B

Rationale: The correct answer is B: Cervix. The cervix is the narrow passage that connects the uterus to the vagina. It acts as a barrier between the uterus and the outside environment. The other choices are incorrect because: A: Vagina is the birth canal and does not directly connect the ovary to the uterus. C: Fallopian tube connects the ovary to the uterus but does not directly attach to it. D: Perineorrhaphy is a surgical procedure to repair the perineum and is not related to connecting the ovary to the uterus.

Correct Answer: C

Rationale: The correct answer is C: labia. The labia minora are two inner folds that cover and protect the vaginal opening. This is because the labia minora are part of the external female genitalia and specifically designed to provide protection to the vaginal opening. A: Uterus - Incorrect. The uterus is a separate organ and is not involved in covering or protecting the vaginal opening. B: Fallopian tubes - Incorrect. The fallopian tubes are part of the reproductive system but are not located near the vaginal opening or involved in its protection. D: Vagina - Incorrect. While the vagina is connected to the vaginal opening, it is not the structure that directly covers and protects it.

Correct Answer: C

Rationale: The correct answer is C because spermatogenesis occurs within the convoluted seminiferous tubules of the testes. This is where sperm cells are produced through a series of cell divisions and maturation processes. Choice A is incorrect as spermatogenesis does not occur at the level of testicular interstitial cells, which are responsible for hormone production. Choice B is also incorrect as Leydig cells are responsible for testosterone production, not sperm production. Choice D is incorrect as spermatogenesis actually begins during puberty, typically around the age of 12-13, not specifically at the age of 14.