Final answer:
Fine clay and plankton-shell deposits in the deep ocean are known as Abyssal sediments. These consist of muds and skeletons of sea creatures and accumulate mostly near the shoreline.
Step-by-step explanation:
The name given to fine clay and plankton-shell deposits in the deep ocean is b. Abyssal sediments. Abyssal sediments are typically found in the deep ocean basins and are made up of fine particles that have settled out of the water column. These materials are primarily muds and the shells of tiny sea creatures, such as foraminifera and coccolithophores. Sediment thickness tends to be greatest near the shore, where it is transported into the ocean by rivers and wind currents.
Options like basalts, iron formations, and pyroclastic deposits refer to different types of geological materials. Basalts are a type of igneous rock that forms from cooling lava, iron formations are sedimentary rocks rich in iron minerals, and pyroclastic deposits are associated with volcanic activity. Pelagic sediments could have been another answer, as they include abyssal sediments and also refer to deposits in the open ocean, but they were not listed as one of the options.