Concept:Prions are misfolded proteins that cause fatal neurodegenerative diseases like mad cow disease.
Explanation:Mad cow disease, also known as bovine spongiform encephalopathy, is caused by prions.
Prions are infectious protein particles that lack nucleic acids.
They induce normal brain proteins to misfold, leading to brain damage.
Prions are not bacteria, viruses, or fungi.
Therefore, Mycoplasma, viroids, and Aspergillus are incorrect.
Answer:B. prions
