The correct answer is (a) fungus. Mucormycosis is a rare but serious fungal infection that can affect the sinuses, lungs, brain, and other organs. It is most common in people with weakened immune systems, such as those with diabetes, cancer, or organ transplants. The fungus that causes mucormycosis is found in soil and decaying organic matter. It can enter the body through the nose, mouth, or lungs. Symptoms of mucormycosis include fever, cough, shortness of breath, facial pain, and sinus pain. Treatment for mucormycosis includes antifungal medications and surgery to remove infected tissue.
(b) Bacteria are single-celled organisms that are found in soil, water, and the air. They can cause a variety of diseases, including pneumonia, strep throat, and food poisoning.
(c) Viruses are tiny, non-cellular particles that can cause diseases such as the common cold, the flu, and HIV/AIDS.
(d) Protozoa are single-celled organisms that are found in water, soil, and the digestive tracts of animals. Some protozoa can cause diseases such as malaria and giardiasis.