Amoeba and Paramecium belong to which category of organisms?

The correct option is A Protozoa
Organisms that are single-celled, swim in the water and consume food are generally called protozoa. They belong to the kingdom Protista and are classified into different phyla based on how they move. The amoeba, which belongs to the phylum Sarcodina. This single-celled protist can be any shape it wants because its membrane is flexible and it can push its cytoplasm around to change its shape. The word amoeba means to change. Paramecium moves using tiny hair-like structures on its surface called cilia. The paramecium belongs to a whole group of protists that move using cilia, the phylum Ciliophora.

Hence the correct option is A.