## Core Concept
Free radical scavengers, also known as antioxidants, are molecules that neutralize or mop up free radicals, thereby preventing oxidative stress and damage to cells. They play a crucial role in maintaining cellular health and preventing diseases associated with oxidative stress.

## Why the Correct Answer is Right
Glutathione is a well-known antioxidant that acts as a free radical scavenger. It donates electrons to unstable molecules, such as free radicals, to neutralize them, thereby protecting cells from oxidative damage. On the other hand, is not typically classified as a free radical scavenger in the traditional sense like vitamins C and E, beta-carotene, or glutathione. However, without specific details on the options provided, we can infer based on common knowledge of antioxidants.

## Why Each Wrong Option is Incorrect
- **Option A:** If this option represents a known antioxidant such as Vitamin C, Vitamin E, or beta-carotene, then it is incorrect because these are indeed free radical scavengers.
- **Option B:** Similarly, if this option represents another antioxidant like selenium or coenzyme Q10, then it is incorrect for the same reason.
- **Option C:** If this option is another well-known antioxidant, then it too would be incorrect as it would act to scavenge free radicals.

## Clinical Pearl / High-Yield Fact
A key point to remember is that antioxidants can help protect against chronic diseases such as cancer, cardiovascular disease, and neurodegenerative disorders by reducing oxidative stress. Glutathione, in particular, is notable for its role in detoxification and as a critical antioxidant within cells.

## Correct Answer: D.