Sex organs of thallophytes are generally

Which pigment is present in all algae?

The free-living,nitrogen-fixing cyanobacterium which also forms a symbiotic association with the water fern $Azolla$ is.......

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?

The plants in which vascular tissues are absent or poorly developed and well-developed aerenchyma is present,are:

What is $Chlamydomonas$?