The correct answer is D. Monera.
Bacteria are single-celled organisms that do not have a nucleus or any other membrane-bound organelles. They are the most diverse group of organisms on Earth, and they can be found in almost every environment on the planet. Bacteria are classified in the kingdom Monera, which also includes archaea.
Protista are single-celled eukaryotes that are not plants, animals, or fungi. They are a diverse group of organisms that includes algae, protozoa, and slime molds.
Plantae are multicellular eukaryotes that are photosynthetic. They are a diverse group of organisms that includes trees, flowers, and grasses.
Animalia are multicellular eukaryotes that are heterotrophic. They are a diverse group of organisms that includes mammals, birds, fish, and insects.