**Core Concept**
The question tests the understanding of the stability and safety of oral rehydration solutions (ORS) over time, specifically focusing on the duration after which a freshly prepared solution should not be used. This involves knowledge of **pharmacological stability** and **infection control**.

**Why the Correct Answer is Right**
A freshly prepared oral rehydration solution is recommended to be used within a certain timeframe to ensure its efficacy and safety. The World Health Organization (WHO) recommends that ORS should be prepared just before use and consumed within 24 hours if stored in a clean, airtight container in the refrigerator.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the timeframe might be too short for the solution's stability.
**Option B:** Incorrect as it might not align with the recommended usage period.
**Option C:** This could be plausible but needs verification against the correct answer.
**Option D:** This is likely incorrect as it exceeds the commonly recommended timeframe.

**Clinical Pearl / High-Yield Fact**
It's crucial to remember that the primary aim of using ORS is to prevent dehydration, particularly in children suffering from diarrhea. The solution's effectiveness and safety depend on its proper preparation and storage.

**Correct Answer:** D. 24 hours.