**Core Concept**
Reduced osmolarity Oral Rehydration Solution (ORS) is a formulation designed to treat dehydration caused by diarrhea, with a lower sodium concentration compared to the original ORS. The reduced osmolarity ORS was developed to minimize the risk of hypernatremia and hyponatremia while still effectively replacing lost fluids and electrolytes.

**Why the Correct Answer is Right**
The reduced osmolarity ORS contains 75 mmol/L of sodium, which is lower than the original ORS. This decrease in sodium concentration is crucial to prevent hypernatremia, especially in children. The reduced osmolarity ORS also contains 75 mmol/L of glucose, which helps to promote the absorption of sodium and water through the intestinal epithelium. The reduced osmolarity ORS is recommended for the treatment of diarrhea and dehydration in children and adults.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it may be true of reduced osmolarity ORS, but without specific details, it's hard to judge.
**Option B:** This option is incorrect as reduced osmolarity ORS does contain a higher concentration of potassium (20 mmol/L) compared to the original ORS, which is essential for maintaining proper hydration and preventing hypokalemia.
**Option C:** This option is incorrect as reduced osmolarity ORS does contain a higher concentration of citrate (10 mmol/L) compared to the original ORS, which helps to prevent the precipitation of calcium phosphate and maintain proper acid-base balance.
**Option D:** This option is incorrect as reduced osmolarity ORS does contain a higher concentration of chloride (65 mmol/L) compared to the original ORS, which helps to maintain proper fluid balance and prevent the development of hypochloremic alkalosis.

**Clinical Pearl / High-Yield Fact**
The World Health Organization recommends the use of reduced osmolarity ORS for the treatment of diarrhea and dehydration, as it has been shown to be more effective and safer than the original ORS.

**Correct Answer: B. Reduced osmolarity ORS contains 20 mmol/L of potassium.**