how did this happen
how do this happen
pro:rel mod det:dem v
how did this happen ?
h aʊ WORD_BOUNDARY d ɪ d WORD_BOUNDARY ð ɪ s WORD_BOUNDARY h æ p ə n WORD_BOUNDARY
h o w WORD_BOUNDARY d i d WORD_BOUNDARY t h i s WORD_BOUNDARY h a p p e n WORD_BOUNDARY