Final answer:
Manganese nodules are an example of hydrogenous sediments, formed through the precipitation of hydroxide minerals and metals from seawater, and match with option A.
Step-by-step explanation:
The term manganese nodules corresponds to the appropriate phrase hydrogenous sediment, which is option A. These nodules are rounded lumps of hydroxide minerals and other metals found on the ocean floor.
They form through the precipitation of these minerals from seawater, making them hydrogenous, or chemically precipitated, sediments. Hydrogenous sediments like manganese nodules are important because they provide insight into oceanographic and geochemical processes and can contain economically valuable metals such as manganese, copper, nickel, and cobalt.