Final answer:
The onset of Alzheimer's disease symptoms is gradual, with early stages showing slowly progressing symptoms such as memory loss and confusion. It is the late-onset form that is more common, characterized by a subtle and gradual decline. Consequently, the early stages of severe dementia due to Alzheimer's disease are noticeable gradually, not rapidly, unpredictably, or inconspicuously.
Step-by-step explanation:
The question pertains to the early stages of neurocognitive disorder due to Alzheimer's disease, specifically severe dementia. The onset of early symptoms in Alzheimer's disease, such as disruptive memory loss, confusion about time or place, and difficulty with planning and executing tasks, tends to be gradual. In contrast to the early onset form of Alzheimer's disease marked by genetic mutations and rapid progression, the more prevalent, late-onset form typically presents subtle and slowly worsening symptoms over time.
As the disease progresses, symptoms initially observed mildly become more pronounced. Patients with moderate Alzheimer's will experience increased memory, language, and cognitive deficits, which continue to escalate into severe dementia where significant brain damage is present. Notably, Alzheimer's disease causes a substantial shrinkage of brain volume, and the loss of neurons is especially severe in advanced stages, which can be visualized through comparisons of a normal brain and that of an Alzheimer's patient as seen in medical imaging.
Therefore, the early stages of severe dementia due to Alzheimer's disease become evident very gradually, aligning with option b in the question.