Answer:
D) mutation
Step-by-step explanation:
The Theory of evolution was given by Charles Darwin in 1859 which suggested that Evolution is the result of the natural selection is the mechanism of evolution.
At the time of Darwin, the DNA and genes were not discovered but only the idea began to come into existence by Mendel.
Later the scientist merged Evolution and Mendel's Theory of inheritance and found that the natural selection takes place at the level of DNA and genes. This theory is known as the modern synthesis Theory. The natural selection takes place due to mutations in the gene which refers to the change in the sequence of DNA due to many factors. These mutations are then selected by nature based on the environment.
Thus, Option-D is the correct answer.