Why Were Asteroids Not Discovered Until the 19th Century

Why were asteroids not discovered until the 19th century?

A) although asteroids are the same size as the planets, they are completely covered with dark dusty material, which means they reflect almost no light
B) in their long looping orbits, it was not until the 19th century that an asteroid came close enough to the Earth to be detectable
C) several asteroids collided with each other in early 1801, calling them to the attention of astronomers
D) asteroids are generally small compared to planets and require a good telescope and patient searching to spot them
E) only after Halley's work did astronomers think to look for the tails which allow us to spot an asteroid