Which one of these is a pioneer species in primary succession?

1. Lichens

2. Trees

3. Grasses

4. Shrubs

Answer: Lichen, algae, and fungi.

Explanation: In primary succession pioneer species like lichen, algae and fungi as well as other abiotic factors like wind and water start to "normalize" the habitat. Primary succession begins on rock formations, such as volcanoes or mountains, or in a place with no organisms or soil.

I learned it in school.