In the life cycle of which group are flagellated cells not formed?

$A$: In $Fucus$,the sporophytic phase is limited to the zygote only.
$R$: In $Fucus$,the sporophytic phase is photosynthetic and independent.

Which plant group is considered 'thalloid' (lacking true roots, stems, and leaves)?

The replicate septum of $Spirogyra$ is characterised by:

From which of the following algae,agar-agar is commercially extracted?
$I.$ Gracilaria $II.$ Fucus $III.$ Sargassum $IV.$ Gelidium $V.$ Turbinaria

Which are the common photosynthetic pigments found in all algae?