Answer:
D. In both the cytosol and the chloroplast
Step-by-step explanation:
Proteins in the chloroplast are synthesized in both the cytosol and the chloroplast itself. Some of the proteins necessary for chloroplast function are synthesized in the cytosol and then transported into the chloroplast. These proteins are encoded by genes in the nuclear genome and are synthesized by ribosomes in the cytosol. Once they are synthesized, they are transported via specialized protein transport systems into the chloroplast. On the other hand, some of the other proteins necessary for chloroplast function are synthesized within the chloroplast itself. These proteins are encoded by genes located in the chloroplast's own genome and are synthesized by ribosomes present in the chloroplast stroma. Therefore, both the cytosol and the chloroplast contribute to the synthesis of proteins required for chloroplast function.