Answer
B.
Work Step by Step
Signal transduction pathways taken an extracellular signal, receive it externally or internally, and then pass the information throughout the cell--what B. says. C. can be excluded since it is the opposite of B., and A. is referring to one potential part of a pathway, not the whole. D. is wrong because it excludes the majority of pathways for which the signal is perceived externally by a cell surface receptor protein.