Which event led to the formation of our solar system?

A galaxy broke apart.

A massive star exploded.

A solar nebula collapsed.

Dark matter materialized.

Answer: A solar nebula collapsed.

Explanation:

The most accepted theory of formation of solar system is collapse of molecular cloud having dust and gas - A solar nebula.

Nebula is the birth place of a star. A solar nebula - where Sun was born formed as the dust and gases started clumping together due to gravity. The gravitational collapse of the nebula led to the beginning of the fusion reaction which marked the birth of the star - the Sun. The remnant mass formed planets, moons, asteroids and other constituents of the solar system.

4.75 billion years ago, a large star near what is now the Solar System went supernova, sending heavy element debris outward into the galaxy. Some of the debris, after traveling long distances through space, collided with a Hydrogen cloud.