Final answer:
Spits and other localized features develop at river mouths or estuaries, often forming from sediment deposition. Estuaries feature variable salinity and have unique ecosystems that can include oysters, which thrive in such environments with their mix of fresh and saltwater.
Step-by-step explanation:
Spits and other localized coastal features typically develop at river mouths or estuaries, which corresponds to option C. These formations are created by the process of sediment deposition, where materials such as sand are carried by the river currents and then deposited when the river meets the larger body of water, forming new land features.
Oysters, a type of marine life found in sedimentary environments, typically dwell in areas where they can attach themselves to surfaces, such as rocks or other oyster shells. These can be found in coastal zones, often within estuaries where there's a mix of fresh and saltwater, and sedimentation is common.
Estuaries are characterized by variable salinity levels because they are where freshwater from rivers and streams mixes with salty ocean water. As such, estuaries offer a dynamic environment with a unique ecosystem. Coastal environments can be subdivided into a variety of sedimentary facies, each with distinctive features such as the type of sediment, the abundance of fossils, and sedimentary structures.