Concept:Houseflies carry disease-causing germs from faeces and dirty materials to food and surfaces.Explanation:Cholera is spread through contaminated food and water. Houseflies can carry cholera germs from infected faeces to food, so they are agents for its spread.Malaria is spread by mosquitoes, not houseflies.Measles is spread by droplets from an infected person.Tuberculosis is spread through the air by coughing or sneezing.Answer:A. cholera.