Answer:
D) Typhus fever
Explanation:
Typhus fever is a group of infectious disease which includes different types of typhus like scrub typhus and murine typhus. The typhus disease is spread by the lice and fleas which carries the typhus causing bacteria.
The typhus disease killed almost 3 million people before and during World War I, so the research on the typhus showed that disease is caused by the lice and other fleas. Although vaccine was prepared during World War II, to control the disease DDT was sprayed to kill the lice as an insecticide.
Thus, Option-D is the correct answer.