Why would a writer choose to introduce a direct quotation with a colon?

In this excerpt from "a modest proposal" by jonathan swift, which important issue does the writer deal with using a satirical tone? some persons of a desponding spirit are in great concern about that vast number of poor people, who are aged, diseased, or maimed; and i have been desired to employ my thoughts what course may be taken, to ease the nation of so grievous an incumbrance. but i am not in the least pain upon that matter, because it is very well known, that they are every day dying, and rotting, by cold and famine, and filth, and vermin, as fast as can be reasonably expected. and as to the young labourers, they are now in almost as hopeful a condition. they cannot get work, and consequently pine away from want of nourishment, to a degree, that if at any time they are accidentally hired to common labour, they have not strength to perform it, and thus the country and themselves are happily delivered from the evils to come. a. old, sickly people cannot be hired as laborers because they don't have the physical stamina required for the job. b. old, sickly people and young laborers are useless to the nation because they cannot be productive citizens. c. the economy of the nation is burdened by the poor, the old, and the sickly who survive on charity and handouts. d. the living conditions of the poor and their lack of employment opportunities are serious concerns for the nation. reset next