Characteristic spores of diatoms are

Which organism is structurally and functionally unicellular?

In which group of organisms does the cell wall form two thin overlapping shells that fit together?

In which of the following is a contractile vacuole present?

Which one is the largest unicellular organism?

Select the correct option for the following statements:
$(i)$ The sea appears red or golden when red dinoflagellates multiply rapidly.
$(ii)$ $Euglena$ / $Slime$ $molds$ are saprophytic protists.