Which pair of words from the excerpt is an oxymoron

In the poem "we wear the mask," paul laurence dunbar voices his repressed anger and frustration toward american society. he repeats the title phrase three times in the poem, using the words mask and we to show that the first use of the phrase is matter-of-fact. in the second stanza, the statement is followed by a period, which shows resignation. however, at the end of the poem, dunbar almost shouts the phrase defiantly. the mask seems to become something he wears proudly. through this gradual emphasis on the phrase, dunbar could be implying that