son difíciles o no
son difíciles o no ?
s o̞ n WORD_BOUNDARY d i f i s i l e̞ s WORD_BOUNDARY o̞ WORD_BOUNDARY n o̞ WORD_BOUNDARY
s o n WORD_BOUNDARY d i f í c i l e s WORD_BOUNDARY o WORD_BOUNDARY n o WORD_BOUNDARY ? WORD_BOUNDARY