Which statement about the Golgi's role in protein processing is true?

• A. The Golgi receives proteins synthesized in the ER and adds modifications and packages them for delivery; sequential cis to trans passage through cisternae is typical.
• B. The Golgi produces ribosomes that traffic to rough ER.
• C. The Golgi is primarily ATP production site in secretory cells.
• D. The Golgi packages proteins in the cytosol without any modifications.

Answer: (A)

Proteins made in the ER are sent to the Golgi, where they undergo further chemical modifications (like glycosylation) and are then packaged into vesicles for delivery to final destinations such as the cell surface, lysosomes, or secreted outside the cell. The Golgi is organized into cis, medial, and trans regions, and proteins typically travel in the direction from cis to trans, undergoing stepwise processing as they move through the stacked cisternae.

This description matches the statement because it correctly describes receiving from the ER, adding modifications, and packaging for targeted delivery, with the characteristic cis-to-trans progression through Golgi compartments. The other ideas mix in functions from other organelles or omit the essential processing and sorting role, such as ribosome production (nucleolus/rough ER), ATP generation (mitochondria), or packaging without any modification (the Golgi actively modifies before packaging).