Final answer:
Sentences about selling children as commodities demonstrate that Jonathan Swift's 'A Modest Proposal' uses the harsh, bitter satire known as Juvenalian, not the milder Horatian satire.
Step-by-step explanation:
Sentences such as "I am assured by our merchants, that a boy or a girl before twelve years old, is no saleable commodity, and even when they come to this age, they will not yield above three pounds, or three pounds and half a crown at most..." make it clear that Swift's satire in "A Modest Proposal" is not Horatian but Juvenalian. The stark, bitter satire presented in Swift's proposal to alleviate the plight of the Irish poor by selling their children as food for the rich strongly contrasts with the mild and playful ridicule of Horatian satire. Instead, it uses the harsh, dark humor characteristic of Juvenalian satire to attack social evils aggressively.