**Core Concept**
Celiac sprue, also known as celiac disease, is a chronic autoimmune disorder where the ingestion of gluten leads to damage in the small intestine. The only effective treatment for celiac disease is a strict adherence to a gluten-free diet.

**Why the Correct Answer is Right**
The gluten-free diet in celiac sprue excludes all products containing gluten, a protein found in wheat, barley, and rye. This is because the immune response to gluten in individuals with celiac disease causes inflammation and damage to the villi in the small intestine, impairing nutrient absorption. The diet is designed to prevent any exposure to gluten, thereby reducing or eliminating symptoms and preventing complications.

**Why Each Wrong Option is Incorrect**
**Option A:** Rice is not inherently gluten-free, as it can be processed in facilities that also handle gluten-containing grains. However, rice itself is generally considered safe for individuals with celiac disease.

**Option B:** Oats are sometimes included in a gluten-free diet, but they must be processed in facilities that do not handle gluten-containing grains. Some oats may still contain trace amounts of gluten.

**Option C:** While fruits and vegetables are naturally gluten-free, they can be contaminated with gluten during processing or preparation. However, in their raw form, they are generally safe for individuals with celiac disease.

**Clinical Pearl / High-Yield Fact**
It's essential to note that gluten-free certification is not regulated in the same way as other food labeling, so always verify the gluten-free status of products with the manufacturer.

**Correct Answer:** C.