Two subgroups of a population separated by a river are rejoined when a drought causes the river to run dry. Assuming that speciation has not yet
occurred, what is true about the two subgroups?
A. Speciation will not occur if individuals in different subgroups can
freely mate and have fertile offspring.
B. The two subgroups will still be reproductively isolated and unable
to mate.
C. New traits that resulted from mutation will not flow between the
subgroups.
D. Speciation will speed up since there will be more competition
between the subgroups