Final answer:
Escherichia in Escherichia coli represents the genus level of classification, and it belongs to the phylum Proteobacteria within the domain Bacteria. It is a prokaryotic organism. The correct option is A.
Step-by-step explanation:
For the organism Escherichia coli, Escherichia represents the genus level of classification. When classifying organisms, the two-part scientific name consists of the genus name followed by the species name. Escherichia coli is often abbreviated to E. coli after its first mention.
Proteobacteria, to which E. coli belongs, is classified at the phylum level within the domain Bacteria. Moreover, E. coli is an example of an organism in the domain Bacteria that has a prokaryotic cell structure.