Which statement describes how organelles aid in transporting proteins in eukaryotic cells?
 A. Mitochondria transport ribosomes to the endoplasmic reticulum.
 B. Lysosomes attach free-floating amino acids to mRNA molecules.
 C. The Golgi apparatus joins free-floating phosphates to ADP molecules.
 D. Membrane-enclosed proteins leave the ER and merge with the Golgi apparatus for further processing.