**Core Concept**
The question is testing the knowledge of preservatives used in toxicological specimens. In toxicology, preserving the specimen is crucial to maintain the integrity of the sample and prevent degradation of the analyte. Preservatives are chemicals added to the specimen to prevent or slow down the degradation process.

**Why the Correct Answer is Right**
The correct answer is likely **Para-Phenylenediamine (PPD)**, which is a commonly used preservative in toxicological specimens. PPD prevents the growth of bacteria and fungi, thereby maintaining the integrity of the sample. It is particularly useful in specimens containing volatile substances, such as blood and urine, where degradation can occur quickly.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it is not a commonly used preservative in toxicological specimens. **Option B:** This option is also incorrect as it is not a suitable preservative for toxicological specimens. **Option C:** This option is incorrect as it is not a widely used preservative in toxicology.

**Clinical Pearl / High-Yield Fact**
It is essential to note that the preservative used in toxicological specimens can affect the results of the analysis. Therefore, it is crucial to use the correct preservative to ensure accurate results.

**Correct Answer: C. Ethyl alcohol