An organism that has been extensively used to test the chromosomes theory of her...

The question is asking which organism has been extensively used to test the chromosomes theory of heredity. The answer is Option A, which is Drosophila melanogaster. Drosophila melanogaster is a type of fruit fly that has been extensively studied by geneticists because it has a relatively short life cycle and produces many offspring. This makes it easy to observe and study the effects of genetic mutations and variations.

The chromosome theory of heredity is the idea that genes are located on chromosomes, which are passed down from parents to offspring during reproduction. Drosophila melanogaster was used extensively in the early 1900s by geneticists such as Thomas Hunt Morgan to study this theory. Morgan and his colleagues were able to observe and document the effects of genetic mutations in Drosophila, which helped to confirm the chromosome theory of heredity.

It's important to note that while Drosophila melanogaster has been extensively used to study genetics, it is not the only organism that has been studied. Other organisms such as Muscar domestica, Zea mays, and Homo sapiens have also been studied to better understand genetics and heredity. However, Drosophila melanogaster remains an important model organism in genetics research due to its ease of study and well-understood genetics.

In conclusion, the correct answer to the question is Option A, Drosophila melanogaster, which has been extensively used to test the chromosomes theory of heredity.