Hint: A broad and diverse collection of photosynthetic eukaryotic organisms having a thallus like structure is referred to as algae. It's a polyphyletic grouping made up of species from many different clades. Algae can be simply categorized into Microalgae (microscopic algae) and huge sea weeds (macroscopic algae). A prokaryotic group of cyanobacteria which perform photosynthesis is often included with algae and are commonly called blue green algae.
Complete answer: This answer can be solved based on the knowledge of nutritional habits of algae. Most algae are photosynthetic in nature, but there exists certain algae which are parasitic on some plants and are referred to as parasitic algae. Only the Chlorophyta have algae that parasitize terrestrial plants. Some green algae, such as Cephaleuros and Chlorochytrium, may be simply epiphytic or endophytic, or their plant connections may progress to genuine parasitism. Parasitic green algae are found mostly on non-cultivated plants and are often missed due to their inconspicuous appearance. A brief note about one of the common parasitic algae is as follows: Cephaleuros is a parasitic thalloid algae genus that includes about a dozen species. Red rust is its popular name. Specimens can grow up to 10 mm in length. The formation of dichotomous branches occurs. The alga is parasitic on a number of key tropical and subtropical economic plants, including tea, coffee, mango, and guava, inflicting harm restricted to the region of algal development on the leaves (algal leaf spot). Not all but algae of certain genera of the green algae are parasitic.
Note: Algae are photosynthetic creatures that possess chlorophyll, a green photosynthetic pigment. Algae can be either single-celled or multicellular. Because algae lack a well-defined body, they lack features such as roots, branches, and leaves, giving them a thalloid shape. Algae can be found in areas with enough moisture. Asexual and sexual reproduction is possible in algae.