So first things first its c. because when two plates collide it causes a earthquake so u can rule those out and of course no not volcano so that's it u only have c left as your answer choice.
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Magma forms by partial melting of upper mantle and crust. Partial melt means that only a fraction of the available material forms a melt, and that the remainder stays solid. The partial melt rises because of its lower density and ascends through he crust.