From the given options, select the word that correctly substitutes the expression-

“One who is eighty years old”

Octogenarian

The word that correctly substitutes the expression "one who is eighty years old" is octogenarian.

• Eightygenariorn is a misspelling of octogenarian.
• Septuagenarirn is a person who is seventy years old.
• Superannuation is a pension or retirement fund.

An octogenarian is a person who is between the ages of 80 and 89. The word comes from the Latin words "octo," meaning "eight," and "genarius," meaning "born."