What is a sedimentary rock?

A. a type of rock that is formed over long periods of time by layers of silt building up on the floor of a body of water

B. a type of rock formed over long periods of time by the cooling and solidification of molten Earth material

C. a type of rock that is formed in a very short period of time by sudden violent volcanic eruptions into the ocean

D. a type of rock that is formed over long periods of time by the transformation of existing rock types