One plate goes under another in a
a. subduction zone
b. transform fault area
c. seafloor spreading zone
d. region of paleomagnetism

Option (A)

Explanation:

Earth crust is comprised of numerous lithospheric plates. These plates constantly move over the viscous asthenosphere layer. This movement of plates is due to the convection current generated in the mantle due to the radiation of the heat from the earth's core.

This plate motion takes place in three different ways, namely

1) Convergent plate motion

2) Divergent plate motion

3) Transform plate motion

In a convergent plate motion, two plate collides with one another. Due to this collision, the denser plate gets subducted below the less denser plate forming a subduction zone. This region is also known as the Benioff zone.

Hence, the correct answer is option (A).