The correct answer is option 4, Charles Darwin. Charles Darwin is credited with formulating the theory of evolution. He proposed the idea of natural selection, which suggests that species that are better adapted to their environment are more likely to survive and reproduce. This theory was described in detail in Darwin`s book "On the Origin of Species," published in 1859.

Option 1, Louis Pasteur, was a French biologist and chemist who is known for his contributions to the field of microbiology, including the development of the germ theory of disease.

Option 2, Aristotle, was a Greek philosopher who lived from 384 to 322 BCE. Although Aristotle made significant contributions to various fields of study, including biology, his ideas on evolution differ significantly from the theory of evolution put forth by Darwin.

Option 3, Gregor Mendel, was an Austrian monk and biologist who is known as the father of modern genetics. While Mendel`s experiments with pea plants laid the foundation for our understanding of genetics, his work did not directly address the theory of evolution.

Thus, the correct answer is option 4, Charles Darwin. Alert - correct answer should be option 4.