The correct answer for the above question is A. Primary succession.
Lichens, represented by the symbiotic relationship are responsible for primary succession or the establishment of a new site for plant growth.
Explanation; Primary succession takes place in lifeless areas; that is; the regions in which the soil is incapable of sustaining life as a result of factors such as lava flows, newly formed sand dunes, or rocks left from a retreating glacier. Lichens are the pioneer species or the first organisms to colonize bare rock in primary succession. They secrete acids that break down the rock and start the soil production process, as many organism require soil before they can colonize an area.
