“Tuberculosis” is caused by

The correct answer is Bacterium.

Tuberculosis (commonly known as TB) is a highly infectious disease that primarily affects the lungs, although it can also damage other parts of the body such as the kidneys, spine, and brain.
The disease is caused by a specific type of bacterium called Mycobacterium tuberculosis. This bacterium is spread from person to person through microscopic droplets released into the air when an infected person coughs, sneezes, or speaks.

Let us look at why the other options are incorrect:
• Malnutrition: While malnutrition weakens the immune system and makes a person more susceptible to contracting TB, it is not the direct pathogen or cause of the disease.
• Protozoan: Protozoans are single-celled eukaryotic organisms that cause diseases like malaria, not tuberculosis.
• Virus: Viruses cause illnesses such as influenza, COVID-19, and the common cold, but tuberculosis is strictly a bacterial infection.