Final answer:
A spit is the best choice for a formation created through longshore drift, as it is a narrow piece of land made up of sediments like sand or shingle that have been transported and deposited along the coast by the action of the wind and waves.
Step-by-step explanation:
The word that best fits the definition "formed through longshore drift" is c. Spit.
Longshore drift is a geological process that involves the transportation of sediments (like sand) along a coast at an angle to the shoreline, which is dependent on prevailing wind direction, swash and backwash. This movement can result in the formation of geographic features known as spits - a long, narrow piece of land projecting from a coastline into the sea, often occurring at a point where the coast changes direction. These spits are generally composed of sand or shingle that has accumulated due to the action of longshore drift. The process involves sediment being carried along the coast, where the seaward end accrues more sediment, forming the spit. This geologic structure is evidence of the dynamic relationship between the forces that shape shorelines and the resulting sedimentary patterns that become part of the geological record.
The formation of spits can eventually lead to the development of other coastal features, like barrier islands, if they grow large enough. However, in the case of the options provided in the question, a spit is indeed the result of deposition of sediment moved by longshore drift, distinguishing it from the other terms listed, such as erosion, deposition in general, or barrier islands, which are formed through different coastal processes.