he couldn't do it
he could do it
pro:sub mod v pro:per
he couldn't do it .
h iː WORD_BOUNDARY k ʊ d ə n t WORD_BOUNDARY d uː WORD_BOUNDARY ɪ t WORD_BOUNDARY
h e WORD_BOUNDARY c o u l d n ' t WORD_BOUNDARY d o WORD_BOUNDARY i t WORD_BOUNDARY