Correct Answer: D

Rationale: A human zygote contains 22 pairs of autosomes and one pair of sex chromosomes, totaling 46 chromosomes. Therefore, the correct answer is 22. Choices A, B, and C are incorrect because they do not accurately represent the number of autosomes in a human zygote. Option A (46) represents the total number of chromosomes in a human zygote, not the number of autosomes. Option B (44) is incorrect as it does not account for the correct number of autosomes. Option C (23) is inaccurate since it represents the total number of chromosomes in a human gamete, not the number of autosomes in a zygote.

Correct Answer: A

Rationale: Rico's symptoms align with Klinefelter syndrome, which is characterized by an extra X chromosome in males (XXY). Enlarged breasts (gynecomastia), mild mental retardation, learning difficulties, and reduced testosterone production are common features of Klinefelter syndrome. Choice B, Tay-Sachs disease, is a genetic disorder that affects the nervous system and is not associated with the symptoms described. Choice C, Turner syndrome, occurs in females with a missing or partially missing X chromosome and does not fit Rico's profile. Choice D, Down syndrome, is caused by an extra copy of chromosome 21 and typically does not present with the symptoms mentioned for Rico.

Correct Answer: C

Rationale: Sickle-cell anemia is a genetic disorder caused by inheriting two copies of a recessive gene, one from each parent. The correct answer is C. Choice A is incorrect because sickle-cell anemia is not primarily caused by a chromosomal abnormality. Choice B is incorrect as the condition is not linked to a single segment found only on the Y chromosome. Choice D is unrelated as it mentions a decrease in estrogen levels, which is not a cause of sickle-cell anemia.

Correct Answer: C

Rationale: The correct answer is C: 'Evaluation of fetal growth.' A fundal height measurement smaller than expected may indicate intrauterine growth restriction (IUGR), requiring serial ultrasounds to monitor fetal growth. Assessing for congenital anomalies (choice A) is usually done through detailed anatomy scans earlier in pregnancy. Recalculating gestational age (choice B) is typically unnecessary at this stage unless there are concerns about accuracy. Determining fetal presentation (choice D) is usually done closer to term to plan for the mode of delivery.

Correct Answer: B

Rationale: Folic acid deficiency during pregnancy is strongly associated with neural tube defects like spina bifida occulta. Adequate folic acid intake before and during early pregnancy significantly reduces the risk of such complications. Tobacco use (Choice A) is linked to other adverse outcomes but not specifically spina bifida occulta. Short intervals between pregnancies (Choice C) can increase the risk of preterm birth and low birth weight but are not directly linked to spina bifida occulta. Preeclampsia (Choice D) is a hypertensive disorder that poses risks to both the mother and baby but is not the primary factor contributing to spina bifida occulta development.