Occurs at convergent boundaries, where one layer of crust sinks into the asthenosphere when it collides with another layer of crust

Subduction zone

Explanation:

Earth is made up of numerous small and large plates commonly known as the lithospheric plates and are frequently in motion due to the convection current that is generated at the mantle. It is the driving force that allows these plates to move over the asthenosphere layer.

This plate motion takes place in three different ways. They are as follows-

1) Convergent motion

2) Divergent motion

3) Transform motion

In the convergent plate motion, two plates collide with one another. The denser plate gets subducted below the less denser plate. As a result of this, the down-going plate creates a subduction zone and this zone is also known as the subduction zone. As the plate gets further deep into the mantle, dehydration in the plates takes place, and partial melting takes place. Due to this, the magma slowly rises up and forms volcanic and island arcs in the over-riding plate.

b is the best answer for this question.