Suppose We Were to Observe Two Supernovas (Exploding Stars)exploding in the Night

Multiple Choice

Suppose we were to observe two supernovas (exploding stars) exploding in the night sky on a particular night.If one was in the nearby arm of the Milky Way Galaxy while the other was in the Andromeda Galaxy,M31,2 million light-years away from us,which of the following statements concerning the actual explosion times of these supernovas is CORRECT?

A) We know both stars exploded at the same time because we saw the explosions at the same time.
B) We cannot tell which star actually exploded first because both stars are so far away.
C) The supernova in the Andromeda Galaxy actually occurred after the one in our Galaxy.
D) The supernova in the Andromeda Galaxy actually occurred before the one in our Galaxy.