Extreme old age when a man behaves like a fool
A). Dotage
B). Imbecility
C). Young
D). Superannuation
Dotage
One word substitute is Dotage.
Dotage: the period of life in which a person is old and weak.
Imbecility: stupid or inane behavior.
Young: having lived or existed for only a short time.
Superannuation: regular payment made into a fund by an employee towards a future pension.