Correct Answer: B

Rationale: The correct answer is mesoderm. The mesoderm is the middle layer of the embryo that gives rise to the bones, muscles, and other connective tissues. The neural tube (choice A) develops into the nervous system, not bones and muscles. The ectoderm (choice C) forms the skin and nervous system, not bones and muscles. The umbilical cord (choice D) is a structure that connects the developing fetus to the placenta; it is not a layer of the embryo that gives rise to bones and muscles.

Correct Answer: C

Rationale: The correct answer is C. Sickle-cell anemia results from a mutation in the beta-globin gene, causing red blood cells to become sickle-shaped. These misshapen cells can obstruct small blood vessels, leading to reduced oxygen delivery to tissues. Choices A, B, and D are incorrect because sickle-cell anemia is typically managed with treatments such as pain relief medications, hydration, and in severe cases, blood transfusions. It is caused by a specific mutation in the beta-globin gene, not by the inability to metabolize phenylalanine. Additionally, sickle-cell anemia is more prevalent in individuals of African, Mediterranean, Middle Eastern, and Indian descent, not exclusive to any specific gender.

Correct Answer: B

Rationale: Folic acid deficiency during pregnancy is a well-known risk factor for neural tube defects, including spina bifida occulta, making supplementation critical in prenatal care. Folic acid plays a crucial role in neural tube formation during early pregnancy. Short intervals between pregnancies do not directly impact the development of spina bifida occulta. Preeclampsia is a hypertensive disorder of pregnancy and is not directly linked to spina bifida occulta. While tobacco use during pregnancy has various adverse effects, it is not the primary factor influencing the development of spina bifida occulta in newborns.

Correct Answer: D

Rationale: The correct additional assessment for postoperative care of a pregnant woman requiring abdominal surgery for appendicitis is monitoring the fetal heart rate (FHR) and uterine activity. This is crucial due to the presence of the fetus. Continuous fetal and uterine monitoring should be prioritized to ensure the well-being of both the mother and the baby. While assessing I&O levels and the IV site are common postoperative care procedures, they are not specific to the unique needs of a pregnant woman. Evaluating for signs and symptoms of infection is important for any postoperative patient but is not the additional assessment required specifically for a pregnant woman in this scenario. Routine vital signs and incision evaluation are standard components of postoperative care but do not address the specific needs related to the fetus and the uterus in this case.

Correct Answer: C

Rationale: Uterine atony is the most likely cause of bleeding 4 hours after delivery, especially after delivering a macrosomic infant and augmenting labor with oxytocin. Uterine atony is characterized by the inability of the uterine muscles to contract effectively after childbirth, leading to excessive bleeding. The other options, such as retained placental fragments (A), unrepaired vaginal lacerations (B), and puerperal infection (D), are less likely causes of postpartum hemorrhage in this scenario. Retained placental fragments can cause bleeding, but this typically presents earlier than 4 hours postpartum. Unrepaired vaginal lacerations would likely be evident sooner and not typically result in significant bleeding. Puerperal infection is not a common cause of immediate postpartum hemorrhage unless there are other signs of infection present.