Concept:Prokaryotic cells have no true nucleus (the genetic material lies free in the cytoplasm) and no membrane-bound organelles. Eukaryotic cells have a true nucleus enclosed by a nuclear membrane.
Solution:Bacteria: single cells without a nuclear membrane, so they are prokaryotic.
Earthworm: an animal, its cells have true nuclei, so it is eukaryotic.
Fungus: cells have true nuclei, so it is eukaryotic.
Plant: cells have true nuclei and chloroplasts, so it is eukaryotic.
So only bacteria are prokaryotic.
Answer:Option A (Bacteria)