Which mineral element is present in the cell wall of algae?

The cell wall of $Spirogyra$ is composed of:

'Pond silk' is the common name of

Some characters of algae are given below:
$a.$ Floridean starch
$b.$ Sulphated phycocolloids in cell wall
$c.$ Alginic acid
$d.$ Trumpet hypha
$e.$ Haplodiplontic life cycle
$f.$ Isomorphic alternation of generation
$g.$ Fucoxanthin
$h.$ Phycoerythrin
$i.$ Zygotic meiosis
$j.$ Two anterior flagella
Which of the given set of characters belongs to $Laminaria$?

Which of the following organisms has a cell wall composed of galactans?

Laminarin and mannitol of class-$Phaeophyceae$ (brown algae) are: