Answer :

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.

Answer: The correct answer is plankton

Explanation:

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