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

“Happening once in a hundred years”

Centennial

The word that correctly substitutes the expression "happening once in a hundred years" is centennial.

• Bicentennial means "happening once every 200 years."
• Annual means "happening once every year."
• Biennial means "happening once every two years."

A centennial is a celebration of the 100th anniversary of an event or institution. The word comes from the Latin words "centum," meaning "hundred," and "annus," meaning "year."