Final answer:
The three diseases spread by vector transmission are malaria (transmitted by mosquitoes), bubonic plague (transmitted by fleas), and Lyme disease (transmitted by ticks).
Step-by-step explanation:
The diseases that are spread by vector transmission are diseases that are carried from one host to another through a vector, which is an organism that does not cause the disease itself but transmits the infection by conveying pathogens from one host to another. Considering the options provided:
Malaria is transmitted by mosquitoes, specifically the female Anopheles mosquito, which is the vector that spreads the Plasmodium parasites causing malaria.
Bubonic plague is spread by fleas that carry the Yersinia pestis bacteria, which are responsible for the disease.
Lyme disease is caused by the bacterium Borrelia burgdorferi and is transmitted to humans through the bite of infected blacklegged ticks, making ticks the vector here.
Therefore, the three diseases among the options given that are spread by vector transmission are 1) malaria, 2) bubonic plague, and 4) Lyme disease.