Identify the etiologic agent of periodontal disease. Describe the clinical changes associated with gingivitis. Explain the histological features associated with gingivitis.

A) Etiologic agent: Porphyromonas gingivalis; Clinical changes: Swollen, red, and bleeding gums; Histological features: Presence of inflammatory infiltrate composed of lymphocytes and plasma cells in the gingival connective tissue.

B) Etiologic agent: Streptococcus mutans; Clinical changes: Receding gums and loose teeth; Histological features: Hyperplasia of the gingival epithelium with elongation of rete pegs.

C) Etiologic agent: Candida albicans; Clinical changes: Formation of abscesses around teeth; Histological features: Presence of fungal hyphae invading the gingival tissue.

D) Etiologic agent: Actinomyces israelii; Clinical changes: Formation of tartar deposits on teeth surfaces; Histological features: Granulomatous inflammation with sulfur granules in the gingival connective tissue.