Final answer:
In the 1st stage of Alzheimer's disease, cognitive function is unaffected because changes in the brain have not yet impacted functioning, which corresponds to answer d) Cognitive function is unaffected.
Step-by-step explanation:
In the 1st stage of Alzheimer's disease (no impairment/preclinical), cognitive function is generally unaffected which means the correct answer is d) Cognitive function is unaffected. A key aspect of this stage is that while there may be changes happening in the brain, such as the development of amyloid plaques and neurofibrillary tangles, they do not yet have a significant impact on daily functioning. At this early, preclinical stage, individuals do not exhibit the symptoms of Alzheimer's disease such as disruptive memory loss or confusion about time or place that are characteristic of more advanced stages.
The progression of Alzheimer's disease is categorized into three main stages: mild, moderate, and severe. As the disease advances, cognitive deficits become more pronounced. In the moderate stage, patients experience notable memory, language, and cognitive deficits, while in the severe stage, patients may lose the ability to communicate and become fully dependent on others for care.