The correct answer is C. Dotage.
Dotage is a state of senility or extreme old age, when a person behaves like a fool. It is often characterized by forgetfulness, confusion, and a loss of interest in activities that were once enjoyable.
Imbecility is a state of mental retardation, characterized by a low IQ and poor intellectual functioning.
Youth is the period of life between childhood and adulthood, when a person is growing and developing physically, mentally, and emotionally.
Superannuation is the state of being retired from work, usually due to old age.
Dotage is the most likely answer to the question because it is the only option that specifically refers to a state of extreme old age when a person behaves like a fool. The other options do not necessarily refer to old age or foolishness.