Answer:
There are prion-like particles in the brain normally, and when these become abnormal they can cause disease. (Ans. A)
Explanation:
Prions are proteins which can trigger normal proteins to fold abnormally, and they are present in the brain. They are causing many types of neurodegenerative diseases in both humans and animals. Which are known as transmissible spongiform encephalopathies.
Prions can enter the brain with the help of infection, also can arise from the gene mutation that encodes the proteins, and sometimes this affects humans by infected meat.
If a person infected from prion disease, it affects central nervous system tissues like brain, eye tissues and spinal cord.
Mucus would most likely accumulate in the respiratory tract as a result of ciliary destruction.
Pertussis (whooping cough) is a highly contagious respiratory tract infection. A severe hacking cough is followed by the a high-pitched breath intake that sounds like "whoop" in many people. Before the vaccine, whooping cough was thought to be a childhood disease. Whooping cough now primarily affects children who have not received the full course of vaccinations, as well as teenagers and adults whose immunity has waned.
Deaths from whooping cough are uncommon, but most commonly occur in infants. That is why it is critical for pregnant women and others who will have close contact with an infant to be immunized against whooping cough. The best way to avoid pertussis is to get vaccinated. Check that you and your loved ones have received their pertussis vaccines.
To know more about the Pertussis, here
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The answer is number 3 because the species has to adjust rapidly to change their environment.