Which of the following algae produce Carrageen ?

Carrageenan is a family of linear sulfated polysaccharides that are widely used as gelling, thickening, and stabilizing agents in food and other products. These polysaccharides are naturally extracted from certain types of seaweed.

The specific seaweeds that contain carrageenan belong to the red algae group (phylum Rhodophyta). Examples of red algae that are harvested for carrageenan include Chondrus crispus (Irish moss), Eucheuma spp., and Kappaphycus spp.

Other algal groups, such as blue‑green (cyanobacteria), green (Chlorophyta), and brown algae (Phaeophyceae), do not produce carrageenan; instead, they may contain other polysaccharides like agar (red algae) or alginate (brown algae).

Therefore, among the listed options, the correct choice is Red algae, as they are the source of carrageenan.