Question

1. when did the asteroids form?

about 3.5 billion years ago
less than 2 billion years ago
about 6.4 billion years ago
about 4.6 billion years ago

Explanation:

Asteroids are remnants from the early solar system. The solar system, including asteroids, is believed to have formed about 4.6 billion years ago. 3.5 billion years ago is too recent as the solar system's formation (and thus asteroid formation) started earlier. Less than 2 billion years ago is also incorrect as that's much later than the solar system's formation. 6.4 billion years ago is incorrect because the universe itself is about 13.8 billion years old, and the solar system (and asteroids) formed much later than that initial universe - forming event.

Answer:

about 4.6 billion years ago