Question

which of these is the primary site of protein synthesis? mitochondria cytoplasm nucleus ribosomes

Explanation:

Ribosomes are the cellular structures responsible for protein synthesis. They read the mRNA sequence and assemble amino acids into polypeptide chains. Mitochondria are the power - houses of the cell (produce ATP). The nucleus contains the cell's genetic material. The cytoplasm is the fluid part of the cell where many metabolic reactions occur, but ribosomes (which can be free in the cytoplasm or attached to the endoplasmic reticulum) are the actual sites of protein synthesis.

Answer:

ribosomes