Suppose there is an infectious disease at a party. how could doctors tell if the disease was foodborne, airborne, or transmitted person to person?

The doctors could simply monitor the symptoms of an infected person. If the infected person sneezes or coughs, then the virus is likely airborne or transmitted from infected surfaces. If no obvious symptoms that would facilitate transmission are detected, the scientists can test for the presence of the virus in the food and drink at the party. 

The answer would be d. pili