The egg is fertilized in which anatomical structure?

Correct Answer: B

Rationale: The correct answer is B: Uterus. After fertilization, the egg travels through the fallopian tube and implants in the uterus for further development. The vagina is the birth canal, not the site of fertilization. The fallopian tube is where fertilization typically occurs, but the actual implantation of the fertilized egg occurs in the uterus. The cervix is the lower part of the uterus that connects to the vagina and plays a role in pregnancy but is not where fertilization occurs.

Correct Answer: B

Rationale: The correct answer is B: estrogens. Estrogens are the primary hormones responsible for the development of secondary sex characteristics in females, including the formation of the hymen. Estrogens play a crucial role in regulating menstrual cycles, breast development, and overall reproductive health in females. Progesterone (choice D) is primarily involved in regulating the menstrual cycle and supporting pregnancy but is not directly responsible for hymen development. Choices A and C do not provide accurate or relevant information related to the development of secondary sex characteristics or the hymen.

Correct Answer: B

Rationale: The correct answer is B. Primary spermatogonium undergo mitosis to replicate and maintain the diploid chromosome number, then meiosis to reduce the chromosome number, resulting in secondary spermatocytes. Choice A is incorrect as it skips meiosis. Choice C is incorrect as it suggests two meiotic divisions from primary spermatogonium, which is not accurate. Choice D is incorrect because it fails to mention the initial step of mitosis before meiosis in the process.

Correct Answer: A

Rationale: The correct answer is A: just after fertilization. After fertilization, the secondary oocyte completes its second meiotic division, forming a mature ovum and a polar body. This process occurs to ensure the correct chromosome number in the resulting zygote. Choices B, C, and D are incorrect because the completion of the second meiotic division occurs specifically after fertilization, not before or just after ovulation or fertilization.

Correct Answer: D

Rationale: The correct answer is D: 23. Sperm cells are haploid, meaning they contain half the number of chromosomes as normal body cells. In humans, normal body cells have 46 chromosomes (23 pairs), while sperm cells have only 23 chromosomes. This is essential for maintaining the correct chromosome number after fertilization. A: 1 - Incorrect. Sperm cells cannot have only 1 chromosome as they need to contribute genetic material during fertilization. B: 2 - Incorrect. Having only 2 chromosomes would not provide sufficient genetic diversity for offspring. C: 12 - Incorrect. This number does not align with the haploid nature of sperm cells in humans with 23 chromosomes.