**Core Concept**
The term 'protective foods' refers to a category of nutrients that have antioxidant properties and help protect the body from oxidative stress, inflammation, and cellular damage. These foods are rich in vitamins C and E, beta-carotene, and other phytochemicals that scavenge free radicals.

**Why the Correct Answer is Right**
The correct answer, A. Fruits and Vegetables, is known as 'protective foods' because they are rich in antioxidants like vitamin C, vitamin E, and beta-carotene. These compounds help neutralize free radicals, reducing oxidative stress and inflammation in the body. Fruits and vegetables also contain other phytochemicals like polyphenols and flavonoids, which have anti-inflammatory and anti-cancer properties.

**Why Each Wrong Option is Incorrect**
**Option B:** Grains are not typically considered 'protective foods' as they are not rich in antioxidants like fruits and vegetables. While whole grains do contain some antioxidants, they are not as potent as those found in fruits and vegetables.
**Option C:** Dairy products are not typically considered 'protective foods' as they are not rich in antioxidants like fruits and vegetables. However, some dairy products like cheese and yogurt do contain antioxidants like vitamin E and beta-carotene.
**Option D:** Protein sources like meat, poultry, and fish are not typically considered 'protective foods' as they are not rich in antioxidants like fruits and vegetables. However, some protein sources like fish do contain antioxidants like omega-3 fatty acids.

**Clinical Pearl / High-Yield Fact**
A diet rich in fruits and vegetables can help reduce the risk of chronic diseases like heart disease, cancer, and neurodegenerative disorders. Aim to include a variety of colorful fruits and vegetables in your diet to reap their antioxidant benefits.

**Correct Answer:** A. Fruits and Vegetables