Which disturbance would result in primary succession?

Which disturbance would result in primary succession?

a. harvesting wheat by using a combine harvester at the end of the growing season
b. controlled burning to stimulate the growth of forest trees such as sequoia
c. the formation of Surtsey, a volcanic island off of the southern coast of Iceland
d. the effect of a large herd of elephants on the grasses and shrubs in an area