To what world historical event does Boccaccio allude in the following line from his Decameron: "Gathering in those houses where no one had been ill and living was more comfortable, they shut themselves in."(A) the Black Death(B) the Hundred Years War(C) the Great Schism(D) the fall of Rome

Black Death

Explanation:

Giovanni Boccaccio was an Italian writer who wrote The Decameron (story of seven men and three women who flee from their city so as to save themselves from the epidemic). The story is referred to the Black Death of 1348 which Boccaccio witnessed himself in the city of Florence, Italy.  

The given lines: "Gathering in those houses where no one had been ill and living was more comfortable, they shut themselves in" alludes to the tragic event that shook the middle historic period i.e The Black Death unleashing a rampage of death ever recorded in history of Europe with over 50% of population falling prey to it.

Thus, Boccaccio's Decameron wonderfully portrays a story revolving around the ongoing crisis in Europe during his time.