D
The second, or middle, stage of AD is characterized by changes in mood, thinking, and behavior. Hallucinations, agitation, and pacing are common symptoms of this stage of the disease. Responses A, B, and C are incorrect. During the first stage of AD, the major symptom is forgetfulness, especially short-term memory loss. The last stage of AD is characterized by impaired speech and mobility, along with decreased awareness of environment and personal needs.