What is the central irony used to support the satire in the passage?

a) the king prefers a pretentious son to his more sensible siblings.
b) the king finds great value in a son who has little sense.
c) the king is unable to see that shadwell is really a poor choice.
d) the king believes that maturity will build more sense in his son.

mac flecknoe
by john dryden (excerpt)

all humane things are subiect to decay,
and when fate summons, monarch's must obey;
this flecknoe found, who like augustus young,
was call'd to empire, and had govern'd long;
in prose and verse was own'd without dispute,
through all the realms of nonsense, absolute;
this aged prince now flourishing in peace,
and blest with issue of a large increase,
worn out with business, did at length debate,
to settle the succession of the state,
and pond'ring, which of all his sons were fit
to reign, and wage immortal wars, with wit,
cry'd 'tis resov'd (for nature pleads, that he
should only rule, who most resembles me,)
alone my perfect image bears,
mature in dulness from his tender years;
alone of all my sons, is he
who stands confirm'd in full stupidity;
the rest, to some faint meaning make pretence,
but shad-- never deviates into sence;