The gene is responsible for the cat's hearing.
The correct answer here is certainly B. They allow scientists to perform new investigations and test new ideas they may not have been able to do in the past because scientists have been able to do the other 3 options without modern technology.
No genes make up chromosomes. Chromosomes contain DNA sequences and specific sequences aka genes make specific traits.
Taxonomy is the classification of something, especially organisms.
So the answer is D. All living organisms
