In this excerpt from james henry hammond’s speech “cotton is king,” which piece of text uses an analogy to justify the existence of the institution of slavery?

in all social systems there must be a class to do the menial duties, to perform the drudgery of life. that is, a class requiring but a low order of intellect and but little skill. its requisites are vigor, docility, fidelity. such a class you must have, or you would not have that other class which leads progress, civilization, and refinement. it constitutes the very mud-sill of society and of political government; and you might as well attempt to build a house in the air, as to build either the one or the other, except on this mud-sill. fortunately for the south, she found a race adapted to that purpose to her hand. a race inferior to her own, but eminently qualified in temper, in vigor, in docility, in capacity to stand the climate, to answer all her purposes. we use them for our purpose, and call them slaves. we found them slaves by the common "consent of mankind," which, according to cicero, "lex naturae est." the highest proof of what is nature's law. we are old-fashioned at the south yet; slave is a word discarded now by "ears polite; " i will not characterize that class at the north by that term; but you have it; it is there; it is everywhere; it is eternal.

a. such a class you must have, or you would not have that other class which leads progress, civilization, and refinement.

b. we use them for our purpose, and call them slaves.

c. the highest proof of what is nature's law.

d. i will not characterize that class at the north by that term; but you have it; it is there; it is everywhere; it is eternal.