Please help? is the bubonic plague caused by a virus, moneran or protist?

Old terms: Plague is caused by a bacterium. "monera" is an old term that covers both the common bacteria and the archaea, the latter a less-familiar evolutionary side-branch. Protists are eukaryotes (unlike bacteria, they have nuclei like ours) that don't have specialized cells. So the answer to this homework question is "monera" for what it's worth. Try to understand the concepts rather than old words.