Kelps are massive

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

The most advanced group of algae is........

Which of the following is a unicellular and small alga?

The product of conjugation of $Spirogyra$ is called

Which type of algae possesses pear-shaped gametes?