Final answer:
Stage I of Alzheimer's disease is mainly associated with mild forgetfulness, unlike the more severe symptoms seen in advanced stages.
Step-by-step explanation:
The characteristic feature associated with a patient in stage I of Alzheimer's disease is C) Mild forgetfulness. Alzheimer's disease progresses through stages, where early signs include problems like mild forgetfulness, confusion about time and place, and difficulty with certain tasks. It is distinct from profound memory loss or severe cognitive decline, which are seen in the later stages of the disease. The initial symptoms can include problems smelling certain scents and are less severe than the symptoms associated with moderate and severe Alzheimer's, where significant memory loss, cognitive deficits, and loss of motor skills occur.