As far as Alzheimer's researchers know, the primary cause of Alzheimer's disease is:

a. deterioration of neurons that produce the neurotransmitter acetylcholine.

b. pruning or deterioration of unused neurons over the life span.

c. normal aging, although accelerated in some individuals.

d. a lack of education or stimulation earlier in life, compounded by obesity.

a. deterioration of neurons that produce the neurotransmitter acetylcholine.

Explanation:

Alzheimer's disease -

It is a disease associated with memory, it is a type of dementia.

The initial stages of the disease is the remember new things, the day to day task becomes very difficult with time.

During this disease the neurons get deteriorated day by day, which are responsible to produce the acetylcholine.

Hence, the correct statement about Alzheimer's disease is (a).