In “the things they carried”, why is jimmy unsure when martha calls the pebble “a token of her truest feelings”

My pretty rose tree by william blake a flower was offered to me, such a flower as may never bore; but i said, ‘i’ve a pretty rose tree,’ and i passed the sweet flower o’er. then i went to my pretty rose tree, to tend her by day and by night; but my rose turned away with jealousy, and her thorns were my only delight. what is the rhyme scheme of the two stanzas in this poem? a. abba, cdda b. abab, acac c. abab, cddc d. abaa, cddc