The correct option is C Ectocarpus
Male gametes are flagellated in Ectocarpus (Phaeophyceae). The flagella of male gametes play an important role in establishing initial sexual contact with the female gamete. However, in Ectocarpus the female gamete too is flagellated but is different in structure.
In Polysiphonia (Rhodophyceae) flagellated gametes are not observed.
In Anabaena, sexual reproduction through gametes is absent while in Spirogyra sexual reproduction takes place by conjugation wherein male gamete passes through a tube to the adjacent filament. The male gametes here are non-flagellated and show amoeboid movement.