The algal phylum whose members lack motile cells

Explanation

The correct answer is Rhodophyta. Rhodophyta, or red algae, are unique among the algae in that they completely lack flagellated or motile cells at all stages of their life cycle. This is a distinctive feature that sets them apart from other algal groups.In contrast, Euglenophyta often have motile cells equipped with flagella, especially during movement. Chlorophyta, or green algae, frequently have motile stages, such as zoospores and gametes, which possess flagella. Lastly, Phaeophyta, or brown algae, typically have motile gametes that use flagella for movement.