Two populations that are separated by a mountain range can no longer interbreed to produce fertile offspring. this is an example of
a) allopatric speciation
b) niche speciation
c sympatric speciation
d subspecies speciation

a) allopatric speciation  

Explanation:

Allopatric speciation occurs when two populations of a species are separated by a geographical barrier. This geographical barrier, which can be a mountain, desert or forest, for example, causes a spatial separation (allopatry). In this case, we say that a geographic isolation occurred.

When these populations separate, they may undergo different pressures as they are in different areas. These pressures, over time, cause a genetic divergence and, consequently, a possible reproductive isolation. Many consider this type of speciation as the main model of speciation.

an organism's phenotype is the  form of a trait  that it  displays. for  flowercolor, a pea  plant  can  display  a phenotype of purple or white flowers. an organism's  genotype  is the alleles of a gene it contains. based on his data, mendel concluded that a phenotype can be  determined  by more than one  genotype.

because they are eaten by the frog and the frog getseaten by the snake and the snake by the eagle