The correct answer is:
The solar system formed about 9 billion years after the big bang.
To elaborate, the Big Bang occurred approximately 13.8 billion years ago, leading to the formation of the universe. After the Big Bang, the universe went through a series of events, including the formation of the first stars and galaxies. The solar system, specifically, formed about 4.6 billion years ago from the remnants of earlier generations of stars, making it roughly 9 billion years after the Big Bang.