Serious though influenza and malaria are, they are not the biggest killers of the age. That title belongs to the plague or "pestilence." No one knows precisely how many die over the course of the reign but the total is probably around 250,000. In 1565 the people of Bristol count up the plague victims for that year and arrive at the figure of 2,070, almost 20 percent of the population. Ten years later, after another deadly outbreak, they record a further 2,000 fatalities. –The Time Traveler's Guide to Elizabethan England,
Ian Mortimer

How does the passage expand on the central idea "large numbers of Elizabethans died from illness and disease"?

It specifies that malaria was the most dangerous disease in Elizabethan England.
It clarifies that the plague was the biggest killer in Elizabethan England.
It explains the causes of illnesses such as influenza, malaria, and the plague.
It lists the ways to avoid falling ill with plague, influenza, and malaria.