A brush border (striated border or brush border membrane) is the microvilli-covered surface of simple cuboidal epithelium and simple columnar epithelium cells found in certain locations of the body.

The columnar epithelium with brush border cells are present in small intestine which increases the surface area for better absorption of digested food.thus,op A.

Columnar Epithelium with microvilli, also known as the brush border, is found in the intestines.

Intestine:
- The intestines are part of the digestive system and are responsible for the absorption of nutrients from digested food.
- The inner lining of the intestines is composed of a single layer of epithelial cells, which are specialized for absorption and secretion.
- The epithelial cells that line the intestines are columnar in shape and have microvilli on their surface, forming a brush border.
- The microvilli are tiny finger-like projections that increase the surface area of the epithelial cells, allowing for more efficient absorption of nutrients.
- The brush border also contains enzymes that help in the digestion of carbohydrates and proteins.
- The presence of the brush border enhances the absorptive capacity of the intestines, making it an ideal location for nutrient absorption.

Stomach:
- The stomach is responsible for the initial digestion of food.
- The inner lining of the stomach is composed of gastric pits and gastric glands, which secrete gastric juices.
- The epithelial cells in the stomach are mainly of two types: surface mucous cells and gastric gland cells.
- The surface mucous cells secrete mucus that protects the stomach lining from the acidic environment.
- The gastric gland cells secrete hydrochloric acid and enzymes, such as pepsin, which aid in the digestion of proteins.
- The stomach does not have a brush border, as its main function is not absorption but rather the breakdown of food.

Appendix:
- The appendix is a small, finger-like pouch attached to the cecum, which is the first part of the large intestine.
- The inner lining of the appendix is composed of simple columnar epithelium, but it does not have microvilli or a brush border.
- The appendix is not directly involved in absorption or secretion but may play a role in immune function.

Pharynx:
- The pharynx is a muscular tube that connects the nasal and oral cavities to the esophagus.
- The inner lining of the pharynx is composed of stratified squamous epithelium, not columnar epithelium.
- The pharynx is involved in the passage of food and air, but it does not have a brush border.