The correct answer is - A. the leading edges of both plates bend upward.
A subduction zone is is created when two plates, one continental and one oceanic, or two oceanic, are colliding. The denser tectonic plate goes beneath the less dense tectonic plate, thus is going downwards into the mantle layer where it is melted, destroyed, or recycled if you will.
Where there's subduction zones, it is very common to have volcanic activity, as well as very often earthquakes, some of which can be devastating.
