The correct option is C All algae are filamentous
Not all algae are filamentous in nature. The form and size of algae is highly variable, ranging from colonial forms like Volvox and filamentous forms like Ulothrix and Spirogyra. A few of the marine forms such as kelps, form massive plant bodies. They posses chlorophyll and hence are autotrophic in nature. They can be classified based on the pigments present in them like carotenes, xanthophll, chlorophyll. Hence, the incorrect statement is option c.