The correct option is C Uniflagellate gametes - Polysiphonia
Polysiphonia is a red alga, polysiphonous and usually well branched, with some plants reaching a length of about 30 cm.
No motile stage occurs in the entire life cycle of red algae. Their spores and gametes are transported by the water in a passive manner.
Gemma cups contain gemmae which are asexual reproductive structures. They are found in some liverworts like Marchantia.
Brown algae produce biflagellated zoospores.
Chlorella is a unicellular alga.