Which statement accurately describes periodontal disease stages in small animals and the radiographic finding that marks progression?

• A. Stage 1: gingivitis only; Stage 2: early bone loss; Stage 3: moderate bone loss and possible furcation involvement; Stage 4: severe bone loss with tooth mobility. Radiographs show progressive alveolar bone loss.
• B. Stage 1: bone loss with furcation involvement; Stage 2: gingivitis; Stage 3: mobility; Stage 4: resorption; Radiographs show stabilized bone.
• C. Stage 1: no changes; Stage 2: gingival inflammation only; Stage 3: bone loss; Stage 4: tooth loss; Radiographs show no bone loss.
• D. Stage 1: gingivitis only; Stage 2: early bone loss; Stage 3: moderate bone loss with possible furcation involvement; Stage 4: severe bone loss with potential tooth mobility. Radiographs show progressive alveolar bone loss.

Answer: (D)