Slate is formed by the metamorphism of which rock?

Slate is a fine-grained metamorphic rock formed when shale or clay is subjected to low-grade heat and pressure. Limestone changes to marble, sandstone to quartzite, and granite to gneiss. Remembering these pairs of parent and metamorphic rocks is the key to such questions; options that give limestone or sandstone are the classic traps because they too produce metamorphic rocks, but different ones.