Which of the following is the lowest category of classification?

The lowest category of classification is species. In biology, organisms are classified based on their shared characteristics into a hierarchical system of groups, or taxa. The hierarchy of taxa, from the broadest to the most specific, is as follows: kingdom, phylum, class, order, family, genus, and species. Species is the most specific and lowest level of classification. It refers to a group of organisms that share common characteristics and can interbreed to produce fertile offspring. Each species is given a unique scientific name, consisting of two parts: the genus and species name. For example, Homo sapiens is the scientific name for humans, with "Homo" being the genus and "sapiens" being the species.