Solution

Dianoflagellates are unicellular protistan algae with complex cell wall structure. The orderly arrangement of cellulosic plates forms armoured plates known as thecae (sing: theca). Thus, the name armoured algae. Option A is correct. Eugneloids are unicellular flagellated eukaryotes that lack cell wall but have pellicle which is a semi-rigid proteinaceous structure. Option B is incorrect. Calcium carbonate is present in cell wall of red algae; it makes the cell permeable to small molecules but impermeable to macromolecules. Red algae secrete calcium carbonate shells which are accumulated in sea bottom and forms red corals. Cyanobacterial cell wall lack cellulose and is made up of peptidoglycans. Thus, the correct answer is option A.