Correct Answer: C

Rationale: During a hospital stay, preschool children may exhibit regression in behaviors such as bed-wetting due to stress. It is important for parents to understand that this behavior is a common response to the hospital environment and should resolve once the child is back home. Therefore, the correct explanation for the nurse to provide to the parents is choice C. Choice A is incorrect because it inaccurately states that the child is no longer potty-trained. Choice B is incorrect as it assumes a medical issue without evidence. Choice D is incorrect as it dismisses the parents' concerns without addressing the underlying cause of the behavior.

Correct Answer: C

Rationale: Diminished breath sounds in an infant are an abnormal finding and warrant further investigation to rule out conditions like atelectasis or pneumonia.

Correct Answer: B

Rationale: Opisthotonos with pain on flexion is a sign of possible meningitis or other serious neurological conditions, requiring immediate medical evaluation.

Correct Answer: D

Rationale: The most indicative behavior of ADHD is the inability to sit still and constant movement, known as hyperactivity. This behavior is a hallmark symptom of ADHD, making option D the correct choice. Options A, B, and C do not specifically reflect the characteristic hyperactivity associated with ADHD, making them less indicative of the disorder. While option B suggests impulsivity, it is not as specific to ADHD as the hyperactivity described in option D.

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.