In the second setting, we used the same 10 subsamples of Set1 as in CV(Set1) and exploited Set2 (composed of 7,000 question-answer pairs) as additional training data for 10-fold cross validation.
in each fold 16,000 question-answer pairs (9,000 from Set1 and 7,000 from Set2) were used as training data for re-rankers, and all systems were evaluated on the remaining 1,000 questionanswer pair subsample from Set1.