Rocks formed from remains of once-living plants and animals are called :

Sedimentary rocks form when particles in suspension are deposited by air, wind, gravity, or water flows, as well as when weathering and erosion break down a rock into loose materials in a source area, and organic sedimentary rocks form when a large number of living things die and are compressed and cemented.

First, we'll look at the alternatives provided in the question:
A. Organic sedimentary rock: When animals and plants die and are pushed into the soil, organic sedimentary rocks are generated by the cementation of dead materials such as animals and plants.
As an example, consider fossil ferrous limestone and coal.
B. Chemical sedimentary rock: Chemical sedimentary rocks occur when mineral constituents in solution become supersaturated and inorganically precipitate. Chemical rocks are made up of mineral crystals of element minerals that are dissolved in water rather than sedimentary bits.

C. Inorganic sedimentary rock: Inorganic sedimentary rocks are formed by the fragmentation of other rocks. These rocks do not contain any biological organisms.
Inorganic sedimentary rock examples include rocks salt and dolomite.
Clastic sedimentary rocks are made up of fragmented bits or clusters of earlier worn and degraded rocks.
These rocks are classed according to their grain size, clusters, composition, and texture.
According to the definition of all sedimentary rocks, only organic sedimentary rocks are created from the remnants of once-living plants and animals.
As a result, the proper option is (A).