What are the distinguishing characteristics of an asteroid?

A. Asteroids are too small to be planets. They can be as small as dust or as large as 965 kilometers across.
B. Asteroids are small, rocky or metallic objects in space.
C. Asteroids orbit the sun and have enough gravity to be round.
D. Asteroids are made up of ice, gas, and rock. They can leave behind a trail of gas and dust.