## **Core Concept**
The composition of Oral Rehydration Solution (ORS) is crucial for effective rehydration in patients with diarrhea. The solution's efficacy depends on the optimal ratio of glucose to sodium, which facilitates the absorption of fluids and electrolytes through the intestinal mucosa via **co-transport mechanisms**.

## **Why the Correct Answer is Right**
The correct glucose: sodium ratio in the reduced osmolarity ORS, as recommended by the World Health Organization (WHO), is **1:1.75** or approximately **1:2**. This ratio enhances the absorption of sodium and glucose through the intestinal brush border membrane by utilizing the sodium-glucose cotransporter 1 (SGLT1). This mechanism is essential for the efficient rehydration of patients with cholera or other diarrheal diseases.

## **Why Each Wrong Option is Incorrect**
- **Option A:** A ratio of 1:1 would not be optimal as it deviates from the recommended ratio that effectively utilizes SGLT1 for cotransport of sodium and glucose.
- **Option B:** Similarly, a ratio of 2:1 would not facilitate efficient sodium and glucose absorption as it does not align with the physiological and biochemical requirements.
- **Option D:** A ratio of 3:1 is far from the recommended and physiologically effective ratio.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the reduced osmolarity ORS with a glucose:sodium ratio of **1:1.75** (75 mEq/L glucose and 65 mEq/L sodium) is more effective and safer than the original formula. This change reduces the osmolarity of the solution, making it closer to the osmolarity of body fluids and reducing stool output.

## **Correct Answer:** .