## **Core Concept**
The question tests the understanding of infantile diarrhea management and its complications, specifically focusing on the signs and symptoms that differentiate between various causes of diarrhea in infants. The key concepts here involve recognizing the signs of dehydration and electrolyte imbalance.

## **Why the Correct Answer is Right**
The infant's symptoms, such as watery diarrhea, irritability, doughy skin, and a rapid pulse, suggest a severe form of dehydration and possibly an electrolyte imbalance. The child has been receiving WHO ORS (Oral Rehydration Solution), which is standard for managing dehydration due to diarrhea. However, the presence of doughy skin and severe irritability could indicate an issue with the type of dehydration or an additional complication. The correct answer, **D. Hypernatremia**, is suggested because the symptoms can be indicative of hypernatremic dehydration, a condition where there is an elevated sodium level in the blood. This condition can occur if the ORS used is not properly diluted or if there is an imbalance in the sodium and water absorption in the intestines. Hypernatremia can cause neurological symptoms like irritability and can also lead to changes in skin texture.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is blank and cannot be evaluated.
- **Option B:** This option is blank and cannot be evaluated.
- **Option C:** This option is blank and cannot be evaluated.

## **Clinical Pearl / High-Yield Fact**
A critical point to remember is that the use of ORS must be done carefully, especially in infants, to avoid electrolyte imbalances. Hypernatremia can be particularly dangerous and requires prompt recognition and management. A useful clinical correlation is that doughy skin can be a sign of hypernatremic dehydration, which differentiates it from the typical dry skin seen in isotonic or hyponatremic dehydration.

## **Correct Answer:** D. Hypernatremia.