Correct Answer: C

Rationale: Sickle cell anemia is most commonly found in individuals of African American descent. This is because sickle cell trait provides some protection against malaria, and historically, regions where malaria is or was prevalent have higher rates of sickle cell anemia. Therefore, individuals with African ancestry are at a higher risk of developing sickle cell anemia compared to other populations. Choices A, B, and D are less likely to develop sickle cell anemia due to lower genetic prevalence in their respective populations.

Correct Answer: A

Rationale: The correct answer is A: 'A Rh-negative mother who has an Rh-positive infant.' In cases where the newborn is born post-term, the mismatched Rh factor between the mother (Rh-negative) and the infant (Rh-positive) can lead to hemolytic disease of the newborn. This condition occurs when maternal antibodies attack fetal red blood cells, causing hemolysis. This can result in jaundice, anemia, and other serious complications for the infant. Choices B, C, and D are incorrect because they do not reflect the mismatched Rh factor scenario that poses a risk for hemolytic disease of the newborn.

Correct Answer: A

Rationale: The correct answer is A: 'Continue prenatal vitamins with B12 while breastfeeding.' Vitamin B12 is crucial for lacto-ovo vegetarian mothers to prevent deficiencies in both the mother and the infant. Choice B is incorrect as Lanolin-based nipple cream is safe for use during breastfeeding. Choice C is not necessary unless there are specific indications for iron supplementation. Choice D, weighing the baby weekly, is important for monitoring growth but not specifically related to the mother's diet.

Correct Answer: D

Rationale: The correct answer is D: Absent patellar reflexes. Absent patellar reflexes can indicate magnesium toxicity, a serious condition that requires immediate intervention to prevent respiratory depression or cardiac arrest. Dizziness while standing (choice A) is common in pregnancy but does not specifically indicate magnesium toxicity. Sinus tachycardia (choice B) can be a normal response to magnesium sulfate but does not indicate toxicity. Lower back pain (choice C) is common in pregnancy and not specifically associated with magnesium toxicity.

Correct Answer: B

Rationale: The correct nursing action is to gradually warm the infant under a radiant heat source. The infant is presenting with signs of cold stress, indicated by cyanotic extremities and a low body temperature. Gradual warming is crucial to stabilize the infant's temperature and prevent further complications. Administering oxygen, notifying the pediatrician, or performing a heel-stick are not the priority actions in this scenario and may not address the immediate need to raise the infant's body temperature.