Final answer:
Shale is usually metamorphosed into slate.
Step-by-step explanation:
The correct answer is 2) slate.
Shale is a sedimentary rock that can undergo metamorphism, a process that changes its physical and chemical properties due to heat, pressure, or chemical reactions. When shale undergoes low-grade metamorphism, it is transformed into slate. Slate is a foliated metamorphic rock composed of clay minerals, and it is characterized by its ability to split into thin, flat sheets. Unlike gneiss, marble, and basalt, which are also metamorphic rocks, slate is the specific rock that shale usually metamorphoses into.