Which of the Following Sequences Best Represents the Order of Events

Which of the following sequences best represents the order of events in the cAMP second messenger pathway?

A) cAMP $\rightarrow$ receptor $\rightarrow$ G-protein activation $\rightarrow$ PKA $\rightarrow$ phosphoproteins
B) receptor $\rightarrow$ G-protein activation $\rightarrow$ AC $\rightarrow$ cAMP $\rightarrow$ PKA $\rightarrow$ phosphoproteins
C) AC $\rightarrow$ decreased temperature $\rightarrow$ phospholipid-breakdown $\rightarrow$ cAMP $\rightarrow$ PKA $\rightarrow$ phosphoproteins
D) G-protein activation $\rightarrow$ GDP $\rightarrow$ cGMP $\rightarrow$ cAMP $\rightarrow$ PKA $\rightarrow$ phosphoproteins
E) None of the above.