Which of the following is true about cells? A. Both eukaryotic cells and prokaryotic cells always contain both a true nucleus that is well-defined and organelles that are separated from the cytoplasm by membranes. B. In general, eukaryotic cells do not have a true nucleus or membrane-bound organelles, whereas prokaryotic cells contain both a nucleus and organelles enclosed by membranes. C. Neither prokaryotic cells nor eukaryotic cells ever contain both a true nucleus that is well-defined and organelles that are separated from the cytoplasm by membranes. D. In general, prokaryotic cells do not have a true nucleus or membrane-bound organelles, whereas eukaryotic cells contain both a nucleus and organelles enclosed by membranes.