The correct option is C Spirogyra and Chlorella are examples of filamentous algae
The statement “Spirogyra is an example of filamentous algae” is true. However, Chlorella is a genus of green algae belonging to the division Chlorophyta. These are non-filamentous with spherical cells of about 2 to 10 micrometre in diameter. These do not possess flagella. Hence, statement c is the incorrect one.