None of the above, but B is closest.
Freewill, we cause bad things for ourselves, not God. Also, how do you know something bad doesn't happen to prevent something even worse?
Maybe someone got hit by a bus (bad thing) on his way to go rob a liquor store where he would have killed the cashier and maybe a couple bystanders (worse thing). Or a harsher example, maybe a child dies of leukemia (awful thing) but the kid was going to grow up to be a serial killer or pedophile?
By the way, the "why does God let bad things happen?" question is the lamest thing non-religious people have come up with thus far.