I need help on this question in biology and biology is hard and confusing

b. the new species must be unable to breed with the original species.

Explanation:

By definition, species are defined as groups of similar organisms that can live and breed freely. This means that individuals in that species can interbreed and produce viable, fertile offspring. However, two different species cannot interbreed to produce fertile offspring due to biological barriers known as mechanisms of reproduction isolation.

These barriers are broadly classified as pre and postzygotic. Prezygotic barriers include the following:

Speciation, the production of an entirely new species, requires a maintenance of genetic diversity. Therefore, the new and original species cannot interbreed as this would limit the gene pool and decrease genetic variations.

your answer is "the 1950's"