Suppose an Astronomer Were to Observe Two Supernovas (Exploding Stars)

Suppose an astronomer were to observe two supernovas (exploding stars) in the night sky on a particular night. If one was in the nearby arm of the Milky Way Galaxy, approximately 2000 light years away from Earth, while the other was in the Andromeda Galaxy, M31, 2 million light-years away from Earth, which of these statements concerning the actual explosion times of these supernovas is correct?

A) Both stars exploded at the same time because the explosions were observed at the same time.
B) It is not possible to determine 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.