Which of these is the best description of Alzheimer's disease?

Answer 1

This question can't be adequately answered without quoting from an authoritative source. This is from the DSM-IV-TR and is therefore a definition based on observable symptomology, not physiology:

Dementia of the Alzheimer's Type is the development of multiple cognitive deficits manifested by both-

1. Memory impairment (impaired ability to learn new information or to recall previously learned information).
2. One or more of the following cognitive disturbances: aphasia (language disturbance); apraxia (impaired ability to carry out motor activities despite intact motor function); agnosia (failure to recognize or identify objects despite intact sensory function); disturbance in executive functioning (for example, planning, organizing, sequencing, abstracting).

DSM-IV-TR, copyright 2000 American Psychiatric Association, Arlington, VA. I am including this contribution under the assumption that one brief answer to one question constitutes fair use.

Answer 2

a progressive disease that causes the brain to deteriorate in a continuous process