Which of the following is a unicellular organism?
I. Amoeba
II. Paramecium

A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and eukaryotic organisms. Amoeba is a unicellular organism that has the ability to change its shape. Paramecia are holotrichous ciliates, that is, unicellular organisms in the phylum Ciliophora that are covered with cilia.