Differences between eukaryotic cells and prokaryotic cells are
separate organelles
a cell membrane
an enclosed nucleus
size

The best answer is the third option namely an enclosed nucleus. One major difference between these two types of cells is that a prokaryote cell has no distinct nucleus enclosed with a membrane whereas in a eukaryote cell the genetic material, which is DNA, is packaged into chromosomes and found within a distinct nucleus that is enclosed with a membrane Examples of prokaryotes are bacteria such as staphylococcus species found as commensals on the skin of man and Streptomyces soil bacteria from which the antibiotic streptomycin is derived. Examples of eukaryotes are an amoeba, which is a unicellular protozoan that lives in water and a hepatocyte which is a liver cell in man.

The correct answer is b