Read the following selection from the section “Yersinia pestis: The Black Death.” More commonly, though, it is spread by flea bites. Before feeding, fleas vomit into our bloodstreams. This is how the bacteria spread. The effects of the bubonic plague are just as gross. Soon after infection, the diseased person develops swelling in their body, called buboes. Next, bleeding inside the body causes swellings of pus and blood. This gives the skin strange colors.

What is the structure of this selection?

A
question and answer
B
cause and effect
C
problem and solution
D
comparison