The process that would change metamorphic rock to igneous rock is melting followed by cooling.
The correct answer is "melting followed by cooling". When metamorphic rock is subjected to extreme heat and pressure, it can undergo melting and turn into magma. As the magma cools and solidifies, it forms igneous rock. So, to change metamorphic rock to igneous rock, the process involves the transformation of the rock into molten magma through melting, and then the subsequent cooling and solidification of the magma to form igneous rock.
