Option 1 is the correct answer. Alzheimer`s disease is a disorder of the brain. It is a progressive neurological disorder that impairs memory, thinking, and behavior. It is characterized by the accumulation of plaques and tangles in the brain, which disrupt the communication between nerve cells and eventually lead to the death of brain cells. As a result, individuals with Alzheimer`s disease experience a decline in cognitive abilities, such as memory loss, confusion, difficulty in problem-solving, and changes in behavior and personality. While the exact cause of Alzheimer`s disease is not fully understood, it is believed to be influenced by a combination of genetic, lifestyle, and environmental factors. Currently, there is no cure for Alzheimer`s disease, but there are treatments available to manage the symptoms and slow down the progression of the disease.