An example of a colonial alga is-

The correct option is B

Volvox

The correct option is B

Explanation of correct option

1. Volvox belongs to the polyphyletic genus of chlorophyte green algae and Volvocaceae.
2. These algae form spherical colonies consisting of about 50,000 cells. They are found in various freshwater habitats.

Explanation of incorrect option

Option A

Chlorella is a spherical single-celled green alga from the chlorophyte genus.

Option C

Ulothrix is a green non-branching filamentous alga usually found in both marine and freshwater.

Option D

Spirogyra is a green unbranched filamentous free-floating algae found in freshwater.

Final answer

An example of a colonial alga is Volvox.