**Core Concept**
The World Health Organization (WHO) recommends a specific amount of Oral Rehydration Solution (ORS) to be administered to children with dehydration, based on the severity of dehydration and the child's weight. The goal is to provide adequate fluid and electrolyte replacement to prevent further dehydration.

**Why the Correct Answer is Right**
For children with some dehydration (WHO's mild dehydration), the recommended amount of ORS is 75 mmol/L of sodium. According to the WHO guidelines, the amount of ORS to be given in the first 4 hours is 75 mmol/L of sodium, which is approximately 75-100 mL/kg of ORS. This amount helps to replenish lost fluids and electrolytes, promoting rehydration and preventing further complications.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify the correct amount of sodium in ORS (75 mmol/L) or the correct volume of ORS to be administered.
* **Option B:** This option is incorrect because it does not provide the correct volume of ORS to be administered in the first 4 hours.
* **Option C:** This option is incorrect because it does not provide the correct amount of sodium in ORS (75 mmol/L) or the correct volume of ORS to be administered.

**Clinical Pearl / High-Yield Fact**
For children with mild dehydration, administering 75-100 mL/kg of ORS with 75 mmol/L of sodium in the first 4 hours can help prevent further dehydration and promote rehydration.

**Correct Answer: C. 75 mmol/L of sodium, approximately 75-100 mL/kg of ORS.**