## **Core Concept**
The question pertains to the preservation of alcohol, which involves preventing the growth of microorganisms and oxidation. Various chemicals can be used for this purpose, depending on the type of alcohol and its intended use.

## **Why the Correct Answer is Right**
The correct answer, **. C. Sodium metabisulfite**, is commonly used in the preservation of alcoholic beverages. Sodium metabisulfite acts as an antimicrobial agent and an antioxidant. It releases sulfur dioxide, which has antimicrobial properties and can prevent oxidation, thus preserving the flavor and preventing spoilage of the alcohol.

## **Why Each Wrong Option is Incorrect**
- **Option A:** **Sodium benzoate** is a preservative used in foods and beverages but is more commonly associated with acidic environments like soft drinks and fruit juices, not specifically for alcohol preservation.
- **Option B:** **Potassium sorbate** is another preservative used to inhibit the growth of yeast and mold in foods and beverages, including wines, but it's not the most specific or commonly associated choice for alcohol preservation in general contexts.
- **Option D:** **Copper sulfate** has antimicrobial properties and can be used in various applications, including as an algaecide in water treatment and in some agricultural applications. However, it's not typically used for preserving alcohol due to its toxicity and potential to impart unpleasant flavors.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that **sulfites**, like sodium metabisulfite, are used not only as preservatives but also to prevent **browning** and **spoilage** in foods and beverages, including alcoholic drinks. However, individuals with sulfite sensitivity or sulfite allergy should be cautious.

## **Correct Answer:** . Sodium metabisulfite