Select the option that can be used as a one-word substitute for the given group of words.

A happy development or happening of events by chance.

Serendipity

The word that can be used as a one-word substitute for "a happy development or happening of events by chance" is serendipity.

• Incident is an event that happens, especially one that is unusual or unexpected.
• Suddenly means happening or coming about quickly and unexpectedly.
• Occurrence is the fact of something happening or existing.
• Serendipity is a happy development or happening of events by chance.

Serendipity is the most appropriate word for the given group of words because it specifically refers to a happy development or happening of events by chance. It is derived from the Persian fairy tale The Three Princes of Serendip, which tells the story of three princes who always made fortunate discoveries by accident.