Based on the excerpt, the paragraph expands the central idea about malaria being a deadly disease in the way that Elizabethans were not aware at all of how malaria was spread among people at that time, so because of their lack of knowledge about the illness, they could not find proper treatment to cure it. Thus, the best option that supports the idea is the third sentence "It explains Elizabethan misconceptions about the spread of malaria." Additional support for the idea is that there is no comparison between one disease and another; it is briefly mentioned Romney Marsh with no description; and malaria is not only associated with swampy areas but with tropical areas, too.