Answer:
Infectious diseases are caused by the passing of one person to another. Corona is an example. Noninfectious diseases, they are just spread by pathogens. Good luck!
I think the answer is D. ( or supported by observations ). Because theories change over time, they both NEED to be proven, they do NOT go off of consensus, but they do NEED to be supported by observations.
I hope this helps.
I would say that would be DNA
Hope this helps :)