Which of the following algae produces carpospores?

What type of life cycle is observed in most algae?

Which structure of $Spirogyra$ is flagellated?

The cell wall of $Spirogyra$ is composed of:

Match the following classes of algae with their characteristic colours:
$A.$ Cyanophyceae $a.$ Green colour
$B.$ Chlorophyceae $b.$ Blue-green colour
$C.$ Phaeophyceae $c.$ Red colour
$D.$ Rhodophyceae $d.$ Brown colour

Approximately $9/10$th of the total photosynthesis on Earth is carried out by ...........