Which term describes single-celled photosynthetic organisms?

• A. Unicellular Algae
• B. Rhodophyta
• C. Sea Grass
• D. Agnatha

Answer: (A)

Single-celled photosynthetic organisms are described by the term unicellular algae. Algae perform photosynthesis, and when an organism is made of just one cell, it’s described as unicellular. So this term uniquely pairs the two ideas: photosynthetic capability and a single-cell structure. The other options don’t fit because red algae (Rhodophyta) are mostly multicellular seaweeds, sea grass is a marine flowering plant, and Agnatha are jawless fish that do not photosynthesize.