According to the Nebular Theory,what Are Asteroids and Comets

According to the nebular theory,what are asteroids and comets?

A) They are the shattered remains of collisions between planets.
B) They are the shattered remains of collisions between moons.
C) They are leftover planetesimals that never accreted into planets.
D) They are chunks of rock or ice that condensed long after the planets and moons had formed.
E) They are chunks of rock or ice that were expelled from planets by volcanoes.