Final answer:
The correct answer is (c) Cytosolic proteins, as they are synthesized on free ribosomes in the cytoplasm and remain in the cytosol, unlike secretory, membrane, and nuclear proteins which are synthesized on ER-bound ribosomes.
Step-by-step explanation:
The student's question pertains to the synthesis location of various types of proteins within a cell. Proteins synthesized on cytoplasmic ribosomes include cytosolic proteins, which means the answer to their question is (c) Cytosolic proteins. Secretory proteins, membrane proteins, and nuclear proteins are typically synthesized on bound ribosomes associated with the rough endoplasmic reticulum (ER).
Proteins synthesized on these bound ribosomes are either exported from the cell, embedded in membranes, or targeted to specific organelles and do not remain in the cytosol. In contrast, cytosolic proteins are synthesized on free ribosomes in the cytoplasm and stay within the cytoplasm, functioning there without being transported through the endomembrane system which includes the rough ER and Golgi apparatus.