Correct Answer: D

Rationale: A Z-score of -3.00 indicates that the child's performance is significantly below the average of their peers. It represents an extreme low score, indicating a substantial deviation from the mean performance of the group.

Correct Answer: B

Rationale: The nurse should instruct the parent to expose the infant's skin to air as it helps in promoting the healing process of diaper dermatitis by allowing the skin to breathe and reducing moisture, which can worsen the condition.

Correct Answer: B

Rationale: Taking antibiotics is a contraindication to receiving the MMR vaccine because antibiotics can potentially interfere with the effectiveness of the vaccine. It is essential to avoid administering the MMR vaccine while the child is on antibiotics to ensure the vaccine provides the intended protection.

Correct Answer: B

Rationale: Correct posture after feedings is crucial for an infant with gastroesophageal reflux to reduce the risk of regurgitation. Placing the infant upright helps prevent the backflow of stomach contents into the esophagus, minimizing symptoms of reflux.

Correct Answer: D

Rationale: The 18-month-old child with tachypnea is at the highest risk for dehydration due to increased insensible water loss associated with rapid breathing.