['he', 'find', 'EmptyParameter', 'EmptyParameter', 'EmptyParameter'] ['what', 'happen', 'EmptyParameter', 'they', 'to']
['<PRP>', 'discover-84', 'EmptyParameter', 'EmptyParameter', 'EmptyParameter'] ['what', 'occur-48.3', 'EmptyParameter', '<PRP>', 'to']
He can find out what happened to them.
<PRP> can find out what happened to <PRP>.