The sequence of events in geographic speciation is most likely to be

• A
  Genetic divergence $\rightarrow$ geographic barrier $\rightarrow$ reproductive isolation
• B
  Geographic barrier $\rightarrow$ genetic divergence $\rightarrow$ reproductive isolation
• C
  Reproductive isolation $\rightarrow$ genetic divergence $\rightarrow$ geographic barrier
• D
  Geographic barrier $\rightarrow$ reproductive isolation $\rightarrow$ genetic divergence