Answer:
A.) Geographic isolation happens before speciation.
Step-by-step explanation:
Dobzhansky-Mayr's theory of speciation states that when two populations become geographically isolated, whether because of a geological event, migrations or local extinctions, they evolve separately. After sufficient time for them to accumulate genetic differences, they will be reproductively isolated. If isolation is complete, speciation has occurred
With this we can conclude that the letter A represents an idea derived from Dobzhansky-Mayr's theory of speciation.