How magma is generated in a subduction zone? How magma rising from a subduction zone causes a chain of volcanoes on the surface?

As a tectonic plate slides into the mantle, the hotter layer beneath Earth's crust, the heating releases fluids trapped in the plate. These fluids, such as seawater and carbon dioxide, rise into the upper plate and can partially melt the overlying crust, forming magma. As the magmas are lighter than the mantle and start to rise above the subduction zones to produce a linear belt of volcanoes parallel to the oceanic trench.

Explanation:

the correct answer is 4) heat and pressure

metamorphic rocks arise from transformation of existing rocks types, in a process called metamorphism. during metamorphism the original rock(prolith) change into metamorphic rock by heating (150-200c) and pressure of more than 1000 bar. the original rock can be sedimentary, igneous, or existing metamorphic rock.