D) gas hydrates
Marine sediments can contain significant amounts of methane hydrates, also known as gas hydrates, which are formed when methane gas is trapped within a lattice-like structure of water molecules under conditions of low temperature and high pressure. These gas hydrates are a potential source of energy, as they contain large amounts of methane, which can be extracted and used as a fuel. Although coal and rare-earth elements can also be found in marine sediments, they are not typically associated with energy production in this context. Wind power and ethanol are renewable energy sources, but they are not directly associated with marine sediments.