Here's why:

* Grit is a type of sandstone, which is formed from the accumulation and cementation of sand-sized grains.

* Sedimentary rocks are formed from the accumulation and cementation of sediments, such as sand, mud, and organic matter.

* Igneous rocks are formed from the cooling and solidification of molten rock (magma or lava).

* Metamorphic rocks are formed when existing rocks (igneous, sedimentary, or other metamorphic rocks) are transformed by heat, pressure, or chemical reactions.

Since grit is formed from sand grains, it fits the definition of a sedimentary rock.