Millionaires become eccentric in their old age.

Answer: Option B

Irritable : having or showing a tendency to be easily annoyed.
Peculiar : different to what is normal or expected; strange.
Dull : lacking interest or excitement.
Miserly : of or characteristic of a miser.
Eccentric : (of a person or their behaviour) unconventional and slightly strange.

Synonym of Eccentric is Peculiar