Answer:
one common ancestor
Explanation:
Although Darwin’s theory is often described as the theory of evolution by natural selection, most commentators recognize that common ancestry (the idea that all organisms now alive on earth and all present day fossils trace back to one or a few “original progenitors”) is an important part of the Darwinian picture.
C)
The difference between allele A and allele S is due to changes in the environment.
D-cartilage
Cartilages are soft connective tissues which provide flexibility to certain organs. You can feel it by touching you ear pinna that it is hard and flexible but not fleshy.
Hope I answered the question .