**Core Concept**
The question is inquiring about the specific antioxidant properties of a medication, which is a crucial aspect of pharmacology in medicine. Antioxidants are substances that prevent or slow damage to cells caused by free radicals. In the context of medications, antioxidants can be used to mitigate oxidative stress and inflammation.

**Why the Correct Answer is Right**
The correct answer is **N-Acetylcysteine (NAC)**, which is a well-known antioxidant medication. NAC works by replenishing glutathione stores, a crucial endogenous antioxidant in the body. Glutathione is composed of three amino acids: cysteine, glycine, and glutamine. NAC is a precursor to cysteine, which is then used to synthesize glutathione. This process helps to neutralize free radicals and reduce oxidative stress in the body.

**Why Each Wrong Option is Incorrect**
* **Option A:** **Vitamin C** is indeed an antioxidant, but it is not the most effective or commonly used medication for antioxidant purposes.
* **Option B:** **Vitamin E** is another antioxidant, but it is primarily used as a dietary supplement rather than a medication.
* **Option C:** **Selenium** is an essential mineral with antioxidant properties, but it is not typically used as a medication for antioxidant purposes.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that N-Acetylcysteine has multiple uses beyond its antioxidant properties, including as a mucolytic agent and for its potential benefits in psychiatric disorders such as schizophrenia.

**Correct Answer:** A. N-Acetylcysteine.