Which of the following algae produce Carrageen ?

The correct option/answer is Red algae.

Step-by-Step Explanation:

1. Understanding Carrageen:
Carrageenan (or carrageen) is a family of natural water-soluble sulfated galactans (polysaccharides) extracted from certain species of marine algae. It is widely used in the food, pharmaceutical, and cosmetic industries as a gelling, thickening, and stabilizing agent.

2. Identifying the Source:
Carrageenan is harvested commercially from various species of red algae (Class Rhodophyceae). The most well-known source is Chondrus crispus, commonly referred to as Irish moss, which is a species of red algae. Other major commercial sources include red algae genera like Eucheuma and Kappaphycus.

3. Reviewing the Options:
- Green algae (Chlorophyceae): Do not produce carrageenan; they primarily store starch.
- Brown algae (Phaeophyceae): Produce algin (alginic acid), not carrageenan.
- Red algae (Rhodophyceae): Synthesize and accumulate carrageenan in their cell walls.
- Blue-green algae (Cyanobacteria): Are prokaryotes and do not produce carrageenan.

Therefore, red algae are the primary producers of carrageen.