Answer: B. First ones to appear in an ecosystem with no soil present
Step-by-step explanation:
Primary succession is the process of claiming a previously barren area for living organisms. The area would have no soil and would just be full of rocks having been recently unearthed as a glacier retreated or a lava flows cooled down.
Pioneer species are the first to appear in such an environment. They are able to live on the rocks and sustain themselves. In time, they break down the rocks into soil so that plants are able to grow. Examples of such species include lichens and fungi.