The smooth ER differs from the rough ER in that:
A. The rough ER contains no ribosomes, the smooth ER contains ribosomes.
B. The smooth ER produces carbohydrates and lipids, rough ER produces proteins.
C. The smooth ER produces proteins, rough ER produces lipids.
D. The rough ER is the site of mRNA transcription, smooth ER is the site of protein translation.