Apopulation of animals is split in half by a river. before speciation is completed, the two halves are rejoined when a drought causes the river to run dry. how would this impact the two populations?

a. traits that had developed through mutation would still exist in only one of the halves
b. speciation would still occur because the two halves would be too different genetically to interbreed
c. the two halves would be reproductively isolated
d. gene flow would increase between the two halves, and speciation would not occur

D. Gene flow would increase between the two halves, and speciation would not occur

Explanation:

Speciation is a phenomena of evolution of a new species from the existing parent species. This occurs when the population of the species gets separated due to geographical barrier, behavioral and due to temporal isolation (having distinct mating seasons). The members of the separated populations may undergo with genetic variations and mutations which may likely to produce a new species.

According to the given situation, if the split halves rejoined then speciation would not occur because speciation requires time for genetic variations and mutations to occur. As, a result of rejoining of the two halves the gene flow will occur due to inbreeding and speciation would not occur.

i am positive it is c. condensing but i may be wrong