Question

Influenza is caused by
A. Virus
B. Bacteria
C. Algae
D. Fungus

Answer 1

Influenza also known as flu is a type of infectious disease. It can range from mild to severe. The clinical symptoms are high fever, runny nose, sore throat, muscle and joint pain, headache, coughing, persistent fatigue, and a lethargic feeling.
Influenza can infect the nose, throat, and lungs. It spreads when infected people cough or sneeze leading to the spread of droplets containing viruses into the air which is often called the droplet mode of spread.

Complete answer:
Viruses cause infectious diseases such as the common cold, flu, warts, HIV/AIDS, Ebola, and COVID-19. Viruses invade living, normal host cells, and use these cells to multiply.
Bacteria can cause diseases like Pneumonia, meningitis, and food poisoning. Other Infectious diseases include Cholera by vibrio cholera, Leprosy, and Tuberculosis by Mycobacterium, Syphilis caused by treponema.
Exposure to algae and their toxins can cause diarrhea, nausea, or vomiting; allergies including skin, eye, or throat irritation or breathing difficulties, and food poisoning.
The diseases caused by fungi include Aspergillosis, Blastomycosis. Candidiasis, Coccidioidomycosis, and Fungal Eye Infections. Tinea corporis or ringworm is a type of fungus that causes both jock itch and athlete's foot.

So Option (A), Virus is the correct option.

Note:
Influenza is a type of common viral infection that can be deadly, especially in high-risk groups. high-risk groups include young children, older adults, pregnant women, and people with chronic disease or weak immune systems. fever, chills, muscle aches, cough, congestion, runny nose, headaches, and fatigue are the most common symptoms. The treatment primarily includes proper rest and fluid intake.