## **Core Concept**
The question tests knowledge of minerals with antioxidant properties. Antioxidants are substances that can prevent or slow damage to cells caused by free radicals, unstable molecules that the body produces as a reaction to environmental and other pressures. They are often found in minerals and vitamins.

## **Why the Correct Answer is Right**
Selenium is a mineral that has antioxidant properties. It is a key component of the enzyme glutathione peroxidase, which helps to reduce oxidative stress by converting harmful peroxides into water and alcohol. This action protects cells from damage caused by free radicals.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While crucial for various bodily functions, calcium's primary role is in bone health and signaling, not as an antioxidant.
- **Option B:** Iron is essential for oxygen transport and various enzymatic reactions but does not have a direct antioxidant effect.
- **Option D:** Phosphorus is vital for the formation of DNA, RNA, and ATP, but it is not recognized for antioxidant properties.

## **Clinical Pearl / High-Yield Fact**
A critical point to remember is that selenium deficiency can lead to conditions such as Keshan disease (a form of cardiomyopathy) and Kashin-Beck disease (a joint and bone disorder), highlighting its importance as an antioxidant.

## **Correct Answer Line**
**Correct Answer: C. Selenium**