Antioxidants are

Options

A. hydrating agents
B. dehydrating agents
C. oxidizing agents
D. reducing agents.

Answer

### Step-by-Step Solution:

1. **Understanding Antioxidants**:
- Antioxidants are substances that prevent oxidation. Oxidation is a chemical reaction that can produce free radicals, leading to chain reactions that may damage cells.

2. **Analyzing the Term "Antioxidant"**:
- The prefix "anti-" means against, and "oxidant" refers to oxidation. Therefore, antioxidants are agents that counteract or inhibit oxidation.

3. **Evaluating Options**:
- The question provides several options to identify what antioxidants are:
- **Hydrating Agent**: These substances contain water and help in hydration. They do not prevent oxidation.
- **Dehydrating Agent**: These substances remove water and do not relate to the prevention of oxidation.
- **Oxidizing Agent**: These agents promote oxidation by gaining electrons and oxidizing other substances. This is the opposite of what antioxidants do.
- **Reducing Agent**: These agents donate electrons to other substances, thereby reducing them and preventing oxidation.

4. **Conclusion**:
- Among the options, the reducing agent is the most appropriate answer as it prevents oxidation by reducing other substances while oxidizing itself. Therefore, the correct identification of antioxidants aligns with the properties of reducing agents.

### Final Answer:
Antioxidants are best described as reducing agents, as they prevent oxidation by reducing other substances.