Final answer:
The proper sequence of metamorphic rocks from lowest to highest grade is slate, phyllite, schist, gneiss. These rocks demonstrate increasing degrees of metamorphism marked by a progression in mineral size and foliation.
Step-by-step explanation:
The question is asking about the proper order of metamorphic rocks from lowest to highest grade. The correct sequence is (c) slate, phyllite, schist, gneiss.
These rocks are all foliated metamorphic rocks that form under increasing degrees of metamorphism, which means increasing temperature and pressure conditions. Slate is a low-grade metamorphic rock that forms from shale. Upon further metamorphism, slate can become phyllite, which exhibits a slightly wavy cleavage and a sheen from the fine mica crystals.
With even more metamorphism, phyllite can turn into schist, which is characterized by larger mica crystals and a more pronounced foliation. The highest grade in this sequence is gneiss, which has undergone intense metamorphism to develop distinct banding of light and dark minerals.