Answer: B. Erosion
Step-by-step explanation:
Erosion is a process of removal of top and sub-surface layers of the soil and depositing them to other location. It is caused by physical agents such as water, wind and others.
Among the options given, erosion is the correct option this is because of the fact that erosion due to water will remove the sand and seawalls present on the shorelines. This can only be caused by seawater with high speed water currents.