Final answer:
The correct order of foliated metamorphic rocks from highest to lowest metamorphic grade is gneiss, schist, slate (Option C). Gneiss is the highest grade with distinct banding, schist is medium grade with less pronounced foliation, and slate is low grade with very fine-grained texture.
Step-by-step explanation:
The question is asking to list foliated metamorphic rocks in the order of decreasing metamorphic grade. To answer this, we need to understand that metamorphic grade refers to the degree to which the parent rock has undergone metamorphism.
High-grade metamorphic rocks, like gneiss, have been subjected to higher temperatures and pressures compared to low-grade metamorphic rocks, like slate. Schist falls in between these two in terms of metamorphic grade.
The correct answer to the question is therefore C. gneiss, schist, slate, as this order lists foliated metamorphic rocks from highest to lowest grade. Gneiss is a high-grade metamorphic rock that typically has a banded or layered appearance due to the intense metamorphism causing minerals to segregate into distinct zones.
Schist has a foliated texture that is less distinctly banded than gneiss and usually forms at a medium grade of metamorphism. Finally, slate is the product of low-grade metamorphism of shale and exhibits a very fine-grained foliated texture.