Which of the following organisms lacks self-mobility?

The correct answer is a virus. Viruses are unique entities that require a host cell for their replication and are unable to move or reproduce independently. They consist of a simple structure made up of genetic material (either DNA or RNA) enclosed in a protein coat and, in some cases, an outer lipid envelope. Unlike bacteria, protozoa, and fungi, which can exhibit movement and have cellular structures that allow them to be metabolically active in their environments, viruses do not possess the machinery necessary for metabolic processes or mobility. Instead, they rely entirely on infecting a host organism to propagate.

Bacteria, protozoa, and fungi have their own forms of mobility. Bacteria can move through flagella or cilia, protozoa are often motile through various means like pseudopodia or cilia, and fungi, although primarily stationary, can spread through the growth of hyphae and the release of spores. This fundamental difference in capacity for independent movement and replication distinctly categorizes viruses as lacking self-mobility.