Correct Answer (Detailed Explanation is Below)
A.
Paramecium
Detailed Explanation
Paramecium is a unicellular eukaryotic organism. It has a true nucleus and specialized cellular structures such as cilia, contractile vacuoles and food vacuoles. Bacteria are prokaryotes, while viruses are acellular entities rather than cellular organisms. Important unicellular eukaryotes include
Amoeba, Paramecium, Euglena and yeast.