Answer:
Louis Pasteur was the scientist who confirm that bacteria and other microorganisms is the reason for variety of diseases.
The condensed visible form of chromatin material is called as chromosome.
Is this a multiple choice question or...??
If not, I'd say, that its simple as scientists can easily decipher which variable caused the situations result. And thats because you may have one manipulated variable to be able to know the responding variable.
Genetic Variation is the correct answer. hope it helps!
