Which of the following happens during the process of speciation

The process of speciation is a 2 stage process in which reproductive isolating mechanisms (RIM's) arise between groups of populations.

In Stage 1 : 

a) The gene flow is interrupted between 2 populations  b) This absence of gene flow allows the 2 populations to become genetically distinguished as a consequence to adapting to different local conditions  c) as populations differentiate, RIMs appear because different gene pools are not commonly coadapted d) reproductive isolation appears in the form of postzygotic RIMs: hybrid failure  e) these early RIMs are a byproduct of genetic separation, not directly promoted by natural selection yet 

In Stage 2 : 
a) There is a completion of genetic isolation b) The reproductive isolation develops mostly in the forms of prezygotic RIMs c) The development of prezygotic RIMs is directly developed by natural selection: alleles favoring intraspecific fertility will be increased over time at the expense of interspecific fertilization alleles

Ais the correct answer