Before revision:  To address this lack of comprehensive survey of existing MRC tasks, evaluation metrics  and datasets, herein, (1) we analyzed 57 MRC tasks and datasets ; proposed a more precise classification method of MRC tasks with 4 different attributes  (2) we summarized 9 evaluation metrics of MRC tasks and (3) 7 attributes and 10 characteristics of MRC datasets;
After revision:  To address this lack of comprehensive survey of existing MRC tasks, evaluation metrics and datasets, herein, (1) we analyzed 57 MRC tasks and datasets and propose a more precise classification method of MRC tasks with 4 different attributes (2) we summarized 9 evaluation metrics of MRC tasks and (3) 7 attributes and 10 characteristics of MRC datasets;