Final answer:
A volcanic eruption would most likely be a cause of primary succession, as it can create new landforms or sterilize the land, leading to conditions that require ecological establishment from scratch with pioneer species.
Step-by-step explanation:
The cause of primary succession that is listed among the options is C) volcano. Primary succession is an ecological process where a new land is formed or an area is recolonized after all soil and previous life have been removed, such as through volcanic activity. In contrast, secondary succession refers to the recolonization of an area where soil remains after a disturbance, such as a fire or human activities like farming.
Volcanic eruptions create new landforms or sterilize the land, making it an ideal example of an event that leads to primary succession. Over time, pioneer species, which are often hardy and can establish themselves in such harsh conditions, begin to inhabit the new or sterilized land. This leads to the establishment of ecosystems over time.
Actions such as farming, overhunting, and defoliation typically lead to secondary succession, because while these activities significantly alter the ecosystem, they do not completely remove the soil necessary for life to begin the process of primary succession.