Question

what is the site of protein synthesis? nucleus ribosome mitochondria smooth endoplasmic reticulum (er)

Explanation:

Ribosomes are the sites where amino - acids are assembled into proteins based on the information in mRNA. The nucleus contains DNA but is not the direct site of protein synthesis. Mitochondria are for energy production. The smooth ER is involved in lipid synthesis and detoxification, not protein synthesis.

Answer:

Ribosome