Lipids use most energy, and nucleic acids store RNA and DNA, which is hereditary information. None of the other answer included that, so A should be correct!
I hope this is enough, but I can help more if you'd like!
The first thing that the etiologist can do is try and culture bacteria from the tissue samples in the lab. And then study about the bacterium's properties and characterstics that are leading to causing diseases in the humans.
