The attached gingiva is the type of gingival epithelium that exhibits keratinization. This is an important characteristic that helps the gingiva withstand the mechanical forces and friction encountered during mastication and oral hygiene procedures.

Here is a detailed explanation for each option:

1. Attached gingiva: This area consists of keratinized stratified squamous epithelium. The keratinized layer provides a tough, protective barrier that resists wear and tear. This keratinization is essential because the attached gingiva is firmly bound to the underlying alveolar bone and is subject to constant mechanical stress.

2. Alveolar mucosa: This epithelium is non-keratinized or only partially keratinized. It is more flexible and movable compared to the attached gingiva, allowing the cheek and lips to move freely.

3. Junctional epithelium: This is a thin, non-keratinized epithelium that forms the epithelial attachment to the tooth surface. It provides a seal around the tooth but does not exhibit keratinization.

4. Sulcular epithelium: This epithelium lines the gingival sulcus (the shallow groove between the tooth and free gingiva). It is generally non-keratinized or parakeratinized, which makes it more permeable and less resistant compared to attached gingiva.

In summary, the attached gingiva’s keratinized epithelium plays a vital role in protecting the gingiva from mechanical trauma and maintaining periodontal health.

Reference: Ten Cate’s Oral Histology, 9th Edition, Chapter 5, Page 124