**Core Concept**
The Oral Rehydration Solution (ORS) is a pre-packaged mixture designed to treat dehydration caused by diarrhea, vomiting, and other gastrointestinal disorders. ORS composition is critical in maintaining the balance of electrolytes and fluids in the body, preventing complications such as hyponatremia, hypernatremia, and hypokalemia.

**Why the Correct Answer is Right**
ORS composition typically includes sodium chloride (6.5 grams/L), glucose (13.5 grams/L), potassium chloride (1.5 grams/L), and trisodium citrate dihydrate (2.9 grams/L). The sodium content in ORS is crucial in maintaining the sodium-glucose cotransport mechanism in the small intestine, facilitating the absorption of water and electrolytes. The glucose content is essential for stimulating the sodium-glucose cotransporter, thereby promoting water absorption.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as ORS composition does not typically include lactose.
**Option B:** This option is incorrect as the correct concentration of sodium chloride in ORS is 2.6 grams/L, not 6.5 grams/L.
**Option C:** This option is incorrect as ORS composition does not typically include fructose.
**Option D:** This option is incorrect as ORS composition does not typically include maltose.

**Clinical Pearl / High-Yield Fact**
Remember that ORS composition is a critical aspect of treating dehydration, and the sodium-glucose cotransport mechanism is essential in maintaining electrolyte balance. Always ensure that the ORS is prepared according to the manufacturer's instructions to prevent complications.

**Correct Answer: B. The correct concentration of sodium chloride in ORS is 2.6 grams/L, not 6.5 grams/L.**