How long will it take for the andromeda galaxy to collide with our galaxy?

The collision of the Andromeda and the Milky Way Gallaxy is predicted to happen around 4 billion years from now. Even though it's unlikely that the human race will still exist at the time, if we did, we would likely survive it, as it's likely that the two will merge but that the celestial bodies would not actually colide. 

The answer is a but it also might be 7 so

Answerepicenter;