Final answer:
A decrease in land mass is mostly caused by the process of erosion, which is the natural wearing away of land by water, wind, and ice, as well as by subsidence, which is the downward motion of land. Option d
Step-by-step explanation:
The decrease in land mass can be primarily attributed to the process of erosion. Erosion involves the wearing away of land as a result of various natural forces such as water, wind, and ice. This can be observed in the upper streams of rivers where rocks are eroded and sediment is transported downstream to be deposited on flood plains.
Additionally, we can see the effects of erosion along coastlines where cliffs and caves are formed due to the relentless force of water. The term retrogradation also explains the landward retreat of a shoreline when sedimentation cannot keep pace with subsidence.
Lastly, the process of subsidence, another contributing factor, is the downward motion of land that can occur for several reasons including soil compaction, extraction of resources, or natural geological processes. Option d