Which of the following are known as 'flagellated algae'?

The scientist who created the group Protista for both unicellular plants and animals is

Two species of Amoeba $X$ and $Y$ were kept in fresh water and adapted to it. Species $X$ developed a contractile vacuole. When both were transferred to sea water and adapted,both $X$ and $Y$ lost their contractile vacuole. From these observations,we conclude that:

Mobile animal forms are derived from which of the following?

By what process do organisms of the phylum Protozoa exhibit sexual reproduction?

The contractile vacuole is absent in $......$.