Mad cow disease is caused by:

Correct option is B

Mad cow disease (Bovine Spongiform Encephalopathy, BSE) is caused by  prions, which are misfolded proteins that induce abnormal folding of normal proteins in the brain.
· Unlike bacteria, viruses, fungi, or protozoa, prions are not living organisms but rather infectious proteins.
· They lead to progressive neurological degeneration, characterized by spongiform changes in the brain tissue.
· Prion diseases, including BSE, are known for their long incubation periods and the absence of effective treatments, making them a serious concern in veterinary and human health.