**Core Concept**
The World Health Organization (WHO) revised the Oral Rehydration Solution (ORS) composition in 2002 to improve its efficacy in treating dehydration caused by diarrhea. The revised ORS contains a specific concentration of electrolytes and glucose.

**Why the Correct Answer is Right**
The correct composition of the new ORS is as follows: sodium chloride (NaCl) 2.6 grams per liter, potassium chloride (KCI) 1.5 grams per liter, and glucose 13.5 grams per liter. The total osmolarity of the new ORS is 311 mmol/L, not 300 mmol/L. This increased osmolarity helps to maintain proper fluid balance and electrolyte levels in the body.

**Why Each Wrong Option is Incorrect**
**Option A:** The concentration of sodium chloride (NaCl) in the new ORS is indeed 2.6 grams per liter, which is correct.
**Option B:** The concentration of potassium chloride (KCI) in the new ORS is indeed 1.5 grams per liter, which is correct.
**Option C:** The concentration of glucose in the new ORS is indeed 13.5 grams per liter, which is correct.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the new ORS formulation has a higher osmolarity than the previous one, which helps to improve its efficacy in treating dehydration. This is because the increased osmolarity helps to maintain proper fluid balance and electrolyte levels in the body.

**✓ Correct Answer: D. Total osmolarity - 300 mmol/1**