Which scientist created test that helped confirm that bacteria and other microorganisms cause a variety of diseases

 Louis Pasteur

Louis Pasteur in 1860s, proposed germ theory. The theory was based upon the fact that diseases are caused by the microorganisms. He was officially the first to publish his work.

your answer should be c) enjoy!

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).