17. An apparatus comprising: a processor; and a memory coupled to the processor, wherein the memory comprises instructions which, when executed by the processor, cause the processor to: responsive to identifying an input question as an explanatory question, decompose the explanatory question into one or more explanatory queries; identify one or more passages within a corpus of information that comprise an explanatory clause that provides an explanatory answer to the explanatory question based on pre-determined explanatory clause terms, wherein a passage within the one or more passages within the corpus of information that comprises the explanatory clause is identified by the instructions further causing the processor to: compare each identified clause within a passage to a set of previously identified explanatory clauses; and responsive to the identified clause within a passage corresponding to one of the set of previously identified explanatory clauses, tan the clause within the passage with an ‘EXPLANATORY’ tag; receive hypothesis evidence with one or passages comprising explanatory clauses from the corpus of information; generate one or more candidate explanatory answers based on hypothesis evidence; rank and merge the one or more candidate explanatory answers; and output the one or more candidate explanatory answers.
17. An apparatus comprising: a processor; and a memory coupled to the processor, wherein the memory comprises instructions which, when executed by the processor, cause the processor to: responsive to identifying an input question as an explanatory question, decompose the explanatory question into one or more explanatory queries; identify one or more passages within a corpus of information that comprise an explanatory clause that provides an explanatory answer to the explanatory question based on pre-determined explanatory clause terms, wherein a passage within the one or more passages within the corpus of information that comprises the explanatory clause is identified by the instructions further causing the processor to: compare each identified clause within a passage to a set of previously identified explanatory clauses; and responsive to the identified clause within a passage corresponding to one of the set of previously identified explanatory clauses, tan the clause within the passage with an ‘EXPLANATORY’ tag; receive hypothesis evidence with one or passages comprising explanatory clauses from the corpus of information; generate one or more candidate explanatory answers based on hypothesis evidence; rank and merge the one or more candidate explanatory answers; and output the one or more candidate explanatory answers. 18. The apparatus of claim 17 , wherein the instructions to identify the input question as the explanatory question further causes the processor to: compare the input question to a set of annotated questions in order to identify whether or not the input question is seeking an explanation of an underlying reasoning as to the existence of a particular fact; and responsive to the input question corresponding to one of the set of annotated questions, tag the input question as an ‘EXPLANATORY’ question.