If an Ash Flow Approaches You from the Opposite Side

If an ash flow approaches you from the opposite side of a large hill,are you likely to be safe?

A) Safe. You are fine being behind a hill; ash flows go down valleys.
B) Safe. The ash flow would stop at the hill or go around the sides of it.
C) Safe. You can duck, and it will go over the top of you.
D) Not safe. If you are close to the volcano, fast-moving ash flows can go over nearby hills.
E) Not safe. Even well away from the volcano, when the ash flow reaches the top of a hill, it picks up speed going down the far side, and that takes it to the top of the next hill, and so on.