> Historically, plants were treated as one of two kingdoms including all living things that were not animals, and all algae and fungi were treated as plants. However, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotes (the archaea and bacteria).

I totally agree that it's often used as you describe, but on a test of scientific knowledge, yours is probably not the relevant definition, especially one with questions about bacteria and viruses. In this case, it was though!