Scientists discovered that small-footed and large-footed lizards shared a common ancestor. today they are no longer able to interbreed together.

what is this an example of?

a.
speciation

b.
succession

c.
spontaneous generation

d.
natural selection

I agree that  the answer is speciation

What is speciation: basically what it means is that there is a lack of ability to reproduce because  the two similar species have become different through the process of evolution.

Hopefully this helped and good luck.