Which of the following algae is a blue-green alga?

Give common characteristics of red algae.

$A$ research student collected a certain alga and found that its cells contained both chlorophyll $a$ and chlorophyll $d$,as well as phycoerythrin. The alga belongs to:

Assertion : Red algae contribute to the production of coral reefs.
Reason : Some red algae secrete and deposit calcium carbonate over their walls.

Chloroplasts of $Spirogyra$ have

Which of the following groups of organisms lacks chlorophyll $b$?