Select the option which is the most appropriate one word substitution for the given group of words.

One who is sixty years old

Sexagenarian

The most appropriate one-word substitution for the given group of words "one who is sixty years old" is sexagenarian.

• Octogenarian means someone who is 80 years old or older.
• Septuagenarian means someone who is 70 years old or older.
• Nonagenarian means someone who is 90 years old or older.

The word sexagenarian is the most appropriate because it specifically refers to someone who is 60 years old or older. The other words do not have the same connotation of being in the sixth decade of life.