Which of the following is known as the primitive plant?

Consider the following statements:
$I$. They reproduce asexually by non-motile spores and sexually by non-motile gametes.
$II$. In this class,sexual reproduction is oogamous and accompanied by complex post-fertilisation developments.
$III$. The common members are $Polysiphonia$,$Porphyra$,$Gracilaria$ and $Gelidium$.
The above characteristics belong to which class of algae?

Reproduction in $Spirogyra$ is

Match Column $I$ with Column $II$ and choose the correct option:

Column $I$	Column $II$
$a.$ Shallowest depth	$(i)$ Green algae
$b.$ Intermediate depth	$(ii)$ Brown algae
$c.$ Greatest depth	$(iii)$ Red algae

Spirogyra increases its body length by the division of

On germination,each zygospore of $Spirogyra$ gives rise to: