A 72 yo man fell while shopping and hurt his knee

A 72 yo man fell while shopping and hurt his knee. His vitals are fine. He speaks in a low voice
and is very slow to give answers. What is the most probable dx?
a. Alzheimers
b. Vascular demetia
c. TIA
d. Pseudo-dementia
e. Picks dementia

Ans. The key is A. Alzheimers

Why not other options?
Please explain
Thank you