the answer to your question is c. the density of the magma decreases, your welcome.
Answer:
Option A, The density of the magma decreases.
Explanation:
The mantle of the earth crust melts when the oceanic plate descends into the mantle. The density of this mantle is quite lower than the surrounding rocks and thus it rises upto the surface of earth to form a volcano. However, the pressure beneath the earth crust enables magma to break the rock and gush out of the cracks
