The two pairs of words from these lines that create a paradox that readers must solve to understand the poem's theme are:
C) enthrall, free (because enthrall means to enslave, which is the opposite of free);
and
D) chaste, ravish (because chaste means to abstain from extramarital, or from all, sexual intercourse; and ravish means to give great pleasure to someone or to force a woman to have sex against her wishes.)