Correct Answer: A

Rationale: The correct answer is A. Surfactant therapy is explained to parents as a treatment that enhances the lungs' ability to exchange oxygen and carbon dioxide. This is essential for premature infants with respiratory distress syndrome (RDS) as it helps improve their respiratory function. Choices B, C, and D are incorrect because surfactant therapy primarily focuses on addressing lung function and is not related to sedation, apnea reduction, or fighting respiratory tract infections.

Correct Answer: A

Rationale: Applying a warm compress to the affected ear is a recommended home remedy for earaches as it can help reduce pain and discomfort. The warmth can also help improve circulation and promote drainage if there is fluid buildup. Giving a cold drink (Choice B) is not typically beneficial for earaches and fever. Administering acetaminophen (Choice C) can help reduce fever and alleviate pain, but addressing the earache directly with a warm compress is a more targeted approach. Taking the child to the emergency department (Choice D) is not necessary for a common earache unless there are severe symptoms or complications present.

Correct Answer: B

Rationale: The correct answer is "B: Rolls over." At 6 months, most infants can roll over, which increases the risk of falls. Emphasizing the infant's ability to roll over is crucial to highlight the need for careful supervision and accident prevention. Choices A, C, and D are incorrect because sitting up, crawling short distances, and standing while holding on to furniture typically develop later in an infant's motor skills progression and are not as directly associated with an increased risk of accidents at this stage.

Correct Answer: C

Rationale: Ineffective sucking and swallowing can be early signs of a heart defect like a ventricular septal defect. This is crucial information for the nurse to consider as it aligns with the infant's tentative diagnosis. Choice A is too general and does not provide specific relevance to the situation. Choice B is incorrect as inadequate sucking can indeed be significant, especially in the context of a potential heart defect. Choice D is not directly related to the potential heart defect and feeding difficulties mentioned in the scenario.

Correct Answer: A

Rationale: The correct answer is A: nondisjunction. Trisomy 21, also known as Down syndrome, is caused by nondisjunction, which is an error in cell division leading to an extra copy of chromosome 21. This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome. Choices B, C, and D are incorrect. X-linked recessive inheritance refers to genetic disorders carried on the X chromosome, genomic imprinting involves gene expression based on parental origin, and autosomal dominant inheritance relates to disorders caused by a dominant gene on one of the non-sex chromosomes. In the case of trisomy 21, the cause is specifically related to the error in chromosome division, making nondisjunction the most appropriate answer.