The correct answers are - B. Where oceanic crust meets continental crust, and C. Earthquakes.
Subduction zones appear only on places where a crust of lower density (oceanic crust) meets a crust of higher density (continental crust).
On the places where the oceanic crust meets the continental crust, the oceanic crust goes beneath the continental crust, this makes changes and readjustments in the inner part of the crust, and plus there's significant pressure from the mantle layer from beneath, so earthquakes are a very common occurrence.
