The correct answer is choiceD.

Choice A rationale:

Introducing a regular diet is not the immediate priority for a child with severe diarrhea.The focus should be on stabilizing the child’s condition before reintroducing regular foods.

Choice B rationale:

Maintaining fluid therapy is important, but it is part of the broader goal of managing fluid balance.It is not the first step in addressing severe diarrhea.

Choice C rationale:

Rehydration is crucial, but it falls under the broader category of assessing and managing fluid balance.Ensuring the child is properly hydrated is part of the overall assessment.

Choice D rationale:

Assessing fluid balance is the priority action. This involves evaluating the child’s hydration status, monitoring for signs of dehydration, and ensuring that fluid therapy is appropriately managed.This step is critical to prevent complications from severe diarrhea.

Choice A rationale

Respiratory alkalosis is typically associated with hyperventilation, which can occur in conditions such as anxiety, fever, or certain lung diseases. However, it is less likely in a patient who is nauseous and vomiting.

Choice B rationale

Metabolic alkalosis is a condition that can occur due to the loss of acid from the body, which can happen when a patient is vomiting. When a person vomits, they lose stomach acid (hydrochloric acid), and this can disrupt the acid-base balance in the body, leading to metabolic alkalosis.

Choice C rationale

Metabolic acidosis is typically associated with conditions that cause the accumulation of acid in the body or the loss of bicarbonate, such as kidney disease, lactic acidosis, or certain poisonings. It is less likely in a patient who is nauseous and vomiting.

Choice D rationale

Respiratory acidosis is typically associated with conditions that cause an inability to remove enough carbon dioxide from the body, such as chronic obstructive pulmonary disease (COPD) or airway obstruction. It is less likely in a patient who is nauseous and vomiting.