## **Core Concept**
The question pertains to the management of diarrheal dehydration in children, specifically focusing on the fluid replacement strategy. The **World Health Organization (WHO) plan for the treatment of dehydration** is a widely accepted guideline that provides a framework for the assessment and management of dehydration in children.

## **Why the Correct Answer is Right**
The correct answer, , is based on the WHO's plan for treating dehydration. For children with diarrheal dehydration, the WHO recommends the following fluid replacement regimen:
- **Mild to Moderate Dehydration:** 50-75 mL/kg over 4 hours.
- **Severe Dehydration:** 100 mL/kg over 6 hours, but for the first 4 hours, 75 mL/kg is often considered for severe cases.

However, a commonly used estimate for the amount of fluid to be replaced in the first 4 hours for a child with dehydration due to diarrhoea, especially if not specified as mild, moderate, or severe, can be around 75 mL/kg.

Given the child weighs 12 kg,
75 mL/kg * 12 kg = 900 mL.

## **Why Each Wrong Option is Incorrect**
- **Option A:** . This option suggests 300 mL, which would be inadequate for a 12 kg child based on the standard guidelines.
- **Option B:** . This suggests 600 mL, still lower than what is typically recommended for a child of this weight over 4 hours.
- **Option D:** . This suggests 1200 mL, which might be more fluid than necessary for the initial replacement in many dehydration treatment protocols.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the **WHO plan** for dehydration management emphasizes the importance of using oral rehydration therapy (ORT) for mild to moderate dehydration. For severe dehydration, intravenous fluids may be necessary, but the initial assessment and management plan guide the choice of therapy.

## **Correct Answer:** . 900 mL.