Correct Answer: C

Rationale: A BMI-for-age at the 85th percentile indicates a child is at risk for being overweight, according to the National Center for Health Statistics criteria.

Correct Answer: B

Rationale: The correct answer is B: Lack of surfactant. Respiratory distress syndrome (RDS) in preterm infants is primarily due to a lack of surfactant, which is crucial for keeping the lungs inflated. Without adequate surfactant, the alveoli collapse, leading to breathing difficulties. Choice A, Excessive surfactant, is incorrect as RDS is caused by an insufficient amount of surfactant. Choice C, Immature immune system, and Choice D, Lack of body fat, are not directly related to the development of respiratory distress syndrome in preterm infants.

Correct Answer: A

Rationale: It is appropriate to give a 10-year-old the choice of having a parent present or not during an exam, respecting the child's growing need for privacy.

Correct Answer: C

Rationale: Osteosarcoma is typically treated with a combination of surgery and chemotherapy. This approach aims to remove the tumor and reduce the risk of metastasis. Amputation of the affected extremity may be necessary in some cases to ensure complete removal of the tumor. Intensive radiation is not the primary treatment for osteosarcoma, and bone marrow transplantation is not the standard treatment for this type of cancer.

Correct Answer: B

Rationale: The correct answer is B: 'Observe for projectile vomiting.' Projectile vomiting is a classic sign of pyloric stenosis, caused by obstruction at the pylorus. Choice A is incorrect as metabolic alkalosis, not acidosis, often occurs due to the loss of hydrochloric acid from persistent vomiting. Choice C is incorrect as frequent, small feedings are preferred to prevent overloading the stomach. Choice D is incorrect as placing the infant in an upright position after feeding can help reduce reflux.