One-word substitution (vocabulary): Choose the correct term for “extreme old age when a person behaves like a fool.” Select the single best word that matches the definition exactly.

Given data

• Definition: Extreme old age associated with weakened mental faculties and childish/foolish behavior.
• Options: Imbecility, Senility, Dotage, Superannuation.

Concept/Approach
Dotage specifically denotes the feebleness of mind and childishness often associated with extreme old age.

Reasoning through options
Dotage — the period of life marked by decline of mental faculties; exactly matches the prompt. Imbecility — outdated/pejorative term for severe intellectual disability; not age-specific. Senility — general mental deterioration in old age; close, but the prompt stresses behavior like a fool, for which dotage is the precise idiomatic match. Superannuation — retirement from service due to age; unrelated to foolish behavior.

Final Answer
Dotage