With respect to a given corpus, we call questions with the following property Single Passage Evidence Questions or SEQs: A question Q is a SEQ if evidence E sufficient to select A as an answer to Q can be found in the same text snippet as A.
we call a question that requires multiple different pieces of evidence (in multiple text spans with respect to a corpus) a Cross-passage Evidence Question or CEQ: A question Q is a CEQ if the set of evidence E1, ..., En needed to justify A as an answer to Q cannot be found in a single text snippet containing A, but only in a set of such snippets.