The following table shows the symptoms in four patients. Each patient suffers from a different disease.

Patient Disease Cause Symptom
A Tuberculosis Bacteria Difficulty breathing, coughing
B Polio Virus Paralysis
C Food poisoning Bacteria Stomach cramps, loose stools
D Cystic Fibrosis Hereditary Mucus build up in the lungs

Which patient's respiratory system is affected by an infectious agent?
A
B
C
D

A

Explanation:

Tuberculosis is a bacterial infection caused by Mycobacterium tuberculosis. It is spread via air when affected people cough, sneeze, spit or speak. It mostly affects the lungs, thus, damaging the respiratory system. Affected people have difficulty breathing, produce bloody mucus and have a chronic cough. Antibiotic treatment is used for treating it but many people have developed resistance to the antibiotic treatment, giving rise to a new condition called Multi Drug Resistant Tuberculosis (MDR-TB).