how has that happened
how have that happen
pro:rel aux pro:rel v
how has that happened?
h aʊ WORD_BOUNDARY h ɐ z WORD_BOUNDARY ð æ tʰ WORD_BOUNDARY h æ pʰ ə n d WORD_BOUNDARY
h o w WORD_BOUNDARY h a s WORD_BOUNDARY t h a t WORD_BOUNDARY h a p p e n e d ? WORD_BOUNDARY