Charles darwin
a. proposed natural selection as the mechanism of evolution
b. was the first person to conclude that organisms evolve
c. was the first to realize that fossils are remains of ancient organisms
d. proposed that unused parts of the body deteriorate
e. eagerly published his theory before it was well-developed

Option- A: Is the best option to choose from the given four, as we have the explanation given as below;

Charles Darwin: He was a British naturalist who proposed the theory of biological evolution by natural selection.The mechanism that Darwin proposed for evolution is natural selection.

Explanation:

Darwin’s process of natural selection has four components:

Variation: Organisms (within populations) exhibit individual variation in appearance and behavior. Inheritance:Some traits are consistently passed on from parent to offspring.High rate of population growth:Most populations have more offspring each year than local resources can support leading to a struggle for resources.Differential survival and reproduction: Individuals possessing traits well suited for the struggle for local resources will contribute more offspring to the next generation.