Which of the following does not occur at a subduction zone
a. the leading edges of both plates bend upward.
b. the oceanic crust is pushed down into the mantle.
c. a continental plate moves over an oceanic plate.
d. one oceanic moves beneath another oceanic plate.

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.

not completely sure but i think it’s many moons, smaller in size and a ring system.