Which alga contains B vitamins, calcium, and protein and is cyanobacteria found in lakes and rivers?

• A. Green Algae
• B. Brown Algae
• C. Red Algae
• D. Blue-Green Algae

Answer: (D)

Blue-green algae are cyanobacteria, which are photosynthetic bacteria commonly found in freshwater such as lakes and rivers. They’re often discussed as nutrient-rich sources because they contain B vitamins and protein, and some species also provide minerals like calcium. This matches the description given, since the organism described is cyanobacteria and is associated with freshwater habitats. The other algae groups—green, brown, and red algae—are eukaryotic organisms and are not cyanobacteria, so they don’t fit the description.