Answer: green algae
Explanation:
Alga is classified as plants as it contains chlorophyll. But, it lacks true stem, roots etc. It is a large group of aquatic plants. Algae could be unicellular, multi cellular or colonial.
A unicellular contains single cell where as multi-cellular consists of of many cells. Kelp, Plankton and Brown algae are multi-cellular where as green algae can be either unicellular or multi-cellular.
Symbiosis - mutualism as both benefit from this relationship. Fungi gets food from algae, algae gets protection from fungi.
Plantae is the correct answer
