What form of high-grade metamorphic rock forms at temperatures and pressures where some minerals of the rock begin to melt but the bulk mass of rock remains solid and intact? This rock type is transitional between metamorphic and igneous rock.

A. Garnet
B. Amphibolite
C. Migmatite
D. Eclogite

Option (C)

Explanation:

Migmatite can be defined as metamorphic rock that is formed at high pressure and temperature condition, depicting pro-grade type of metamorphism. This rock is formed from the partial melting of unaltered minerals or those minerals that are slightly modified. But in this process of formation, the bulk mass of the rock remains consistent. It is a transitional rock between the igneous and the metamorphic rock.

Thus, the correct answer is option (C).