The sedimentary rock formed when water deposits tiny particles of clay in very thin, flat layers is called what?

The answer is shale.This requires to check the chapter of sedimentary rocks. Sedimentary rocks are formed from sediments, i.e. tiny pieces from the breaking up of other rocks, and three process by which the pieces of roks transform into new rocks, they are cementation, compactation and recrystallization). There are many kinds of sedimentary rocks, which are classified in three large groups, depending on the kind of sediments and the process of formation: clastic, chemical and organic. Shale sedimentary rocks are just one type from the clastic group. Shales, the most abundant of the sedimentary rocks, are laminated sedimentary rocks from tiny clay grains. Laminated means that they are in layers.

The answer to your question is option a