Multiple choice

The inner planets--Mercury, Venus, Earth and Mars--were formed by

  1. repeated collisions of asteroid-sized debris

  2. collisions with large galaxies

  3. supernovas

  4. masses of cold hydrogen and helium

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The inner terrestrial planets formed through the accretion of planetesimals, which were asteroid-sized bodies of rock and metal colliding over time.