How did the artificial selection practiced by pigeon breeders influence darwin's theory of evolution by natural selection?

a.
darwin concluded that if artificial selection could change a population over time, it could change a population instantly as well.
b.
darwin concluded that if traits in captive pigeons could be selectively passed on to offspring, the selection of traits could also happen in nature.
c.
darwin concluded that if breeders could select for certain traits in pigeons, they could also select for certain traits in saddleback tortoises.
d.
darwin concluded that if pigeons could choose their own traits, then animals in the wild could also choose their own traits.

Option B, Darwin concluded that if traits in captive pigeons could be selectively passed on to offspring, the selection of traits could also happen in nature.

Explanation:

Darwin from the study on pigeon concluded that if certain traits with in the pigeons could be transferred/passed on from one generation to another through artificial or selective crossing then the same thing can be achieved through natural selection but the time required for getting the desired results through natural selection would be high.

In other way if artificial selection causes the passing of certain trait in a given population in an instant time period then the same traits can be passed on through natural selection process over a long time period.

Hence, option B is correct.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).