Correct Answer: A

Rationale: According to the pediatric rule of nines, the head and neck represent 18%, the anterior chest and abdomen 18%, and each arm 9%. By adding these percentages (18% + 18% + 9% + 9% = 45%), we find that 45% of the total body surface area has been burned in this child.

Correct Answer: C

Rationale: When a child ingests a harmful substance like drain cleaner and remains alert with a patent airway and adequate breathing, the initial steps involve contacting poison control to guide further management. In this scenario, providing oxygen to support respiratory function is essential until definitive care is established. Activated charcoal and ipecac are not recommended in the management of ingested caustic substances like drain cleaner. Performing a head-to-toe exam can wait until the child's immediate respiratory needs are addressed and the poison control center has provided guidance on further management.

Correct Answer: D

Rationale: The presence of a large contusion over the left upper quadrant of the abdomen, along with signs of shock, points towards a likely injury to the spleen, especially following trauma. The spleen is located in the left upper quadrant of the abdomen and is susceptible to injury due to its position and vulnerability to blunt trauma.

Correct Answer: D

Rationale: When the top of the baby's head is visible (crowning) during transport, it indicates imminent delivery. In this situation, it is crucial to stop the ambulance and assist with the delivery. This ensures a safe delivery process for the mother and the baby. Waiting to arrive at the hospital or attempting to apply pressure to the baby's head can lead to complications. Allowing the head to deliver and checking for the cord's location is a necessary step during the delivery process, but the immediate priority is to assist in the safe delivery of the baby.

Correct Answer: D

Rationale: Tilting the head back without hyperextending the neck is the safest way to open an infant's airway. Hyperextending the neck can potentially cause harm to the infant, making option D the most appropriate method for opening an infant's airway without suspected neck injury.