## **Core Concept**
The World Health Organization (WHO) Oral Rehydration Solution (ORS) is a type of fluid replacement used to prevent and treat dehydration, especially due to diarrhea. The osmolarity of a solution is a measure of its concentration, which is crucial for the effectiveness and safety of ORS. The osmolarity of ORS has been adjusted over the years to improve its efficacy.

## **Why the Correct Answer is Right**
The correct osmolarity of the new WHO ORS is **245 mOsm/L**. This reduced osmolarity was introduced to decrease the sodium and glucose concentrations from the original formula, which was 311 mOsm/L, to make it safer and more effective for children and adults. The reduced osmolarity ORS has been shown to decrease stool output, vomiting, and the need for intravenous fluids. The new formula contains sodium chloride (NaCl) 2.6 grams/L, glucose, anhydrous 13.5 grams/L, potassium chloride (KCl) 1.5 grams/L, and trisodium citrate dihydrate 2.9 grams/L.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not match the known osmolarity of the new WHO ORS.
- **Option B:** Similarly, this option does not correspond to the updated osmolarity of the WHO ORS.
- **Option D:** This option is also incorrect as it does not align with the reduced osmolarity formulation recommended by the WHO.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the reduced osmolarity ORS with **245 mOsm/L** is recommended for use in treating dehydration caused by diarrhea. This change aims to provide a more effective and safer rehydration solution.

## **Correct Answer:** . **245 mOsm/L**