Final answer:
Patients with TB are most contagious when they cough, as this action spreads infectious droplets through the air.
Step-by-step explanation:
Patients with Tuberculosis (TB) pose the greatest risk for transmitting the disease when they cough. This is because TB bacteria are spread through the air via droplets expelled from the respiratory system. When an infected person coughs, sneezes, or spits, they can expel these droplets containing the Mycobacterium tuberculosis bacteria. These droplets can be inhaled by people nearby, resulting in their infection. TB is primarily a lung disease, but can spread to other parts of the body. Symptoms include a persistent cough with mucus and sometimes coughing up blood. Overcrowded conditions, like those found in industrial cities historically, contributed to its rapid spread, especially among the poor.