Which of the Following Is NOT an Example of How

Which of the following is NOT an example of how differential gene regulation affects cellular response?

A) The expression of proteins that are controlled by signal transduction pathways may vary in different cell types.
B) Cell junctions passing ions between the cytosol of one cell to another cell.
C) A cell may or may not express a receptor for a particular signaling molecule.
D) The expression of proteins involved in intracellular signal transduction pathways may vary in different cell types
E) Different cell types have different cell surface receptors that recognize the same signaling molecules.