What remains left is called a <span>Fossil</span>
I'm not sure what the answer choices are, exactly, but looking up the question I found several other questions with answers, so I'm guessing based on those the choices would be:
1) physical barrier within population
2) extensive gene flow
3) chromosomal changes within population.
Which, in this case, the answer would most likely be 3) chromosomal changes within population.
Genetic engineering is a big thing because of this
