Why Would Astronomers Have Difficulty Spotting a Large Incoming Asteroid

Multiple Choice

Why would astronomers have difficulty spotting a large incoming asteroid headed for Earth?

A) Coming in directly, it remains in position in space, so astronomers cannot see its trajectory.
B) It comes in so fast that they don't have time to see it.
C) It is dark before becoming heated in Earth's atmosphere.
D) Most of them aren't looking for such an incoming body.
E) It would be too big to see.