A prokaryotic cell is a cell without a nucleus (there's more to it, though).
Let's start from the bottom.
Strawberry plant: Plant cells are eukaryotic (cells have nucleus).
Hippopotamus: Animal cells are eukaryotic (cells have nucleus).
Paramecium: That's an animal, and animal cells are eukaryotic (cells have nucleus).
Bacterium: Perfect! Bacterium are prokaryotes! (cells don't have nucleus).
Your answer is bacterium.
Have an awesome day! :)