# A Survey on Machine Reading Comprehension--Tasks, Evaluation Metrics and Benchmark Datasets
## 2 Tasks
### Statistics of MRC Tasks
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Year** & **MRC Tasks** & **Corpus Type** & **Question Type** & **Answer Source** & **Answer Type** \\ \hline
2013 & MCTest [15] & Textual & Natural & Free-Form & Multi-choice \\
2015 & CNN/Daily Mail [19] & Textual & Cloze & Spans & Natural \\
2015 & CuratedTREC [51] & Textual & Natural & Free-Form & Natural \\
2015 & WikiQA [52] & Textual & Natural & Free-Form & Natural \\
2016 & WikiMovies [53] & Textual & Natural & Free-Form & Natural \\
2016 & SQuAD 1.1 [19] & Textual & Natural & Spans & Natural \\
2016 & Who-did-What [48] & Textual & Cloze & Spans & Natural \\
2016 & MS MARCO [39] & Textual & Natural & Free-Form & Natural \\
2016 & NewsQA [54] & Textual & Natural & Spans & Natural \\
2016 & LAMBADA [55] & Textual & Cloze & Free-Form & Natural \\
2016 & WikiReading [56] & Textual & Synthetic & Free-Form & Natural \\
2016 & Facebook CBT [28] & Textual & Cloze & Free-Form & Multi-choice \\
2016 & BookTest [57] & Textual & Cloze & Free-Form & Multi-choice \\
2016 & Google MC-AFP [58] & Textual & Synthetic & Free-Form & Multi-choice \\
2016 & MovieQA [32] & Multi-modal & Natural & Free-Form & Multi-choice \\
2017 & TriviaQA-Web [59] & Textual & Natural & Free-Form & Natural \\
2017 & TriviaQA-Wiki [59] & Textual & Natural & Free-Form & Natural \\
2017 & RACE [60] & Textual & Natural & Free-Form & Multi-choice \\
2017 & Quasar-S [61] & Textual & Cloze & Spans & Multi-choice \\
2017 & Quasar-T [61] & Textual & Natural & Spans & Natural \\
2017 & SearchQA [62] & Textual & Natural & Free-Form & Natural \\
2017 & NarrativeQA [63] & Textual & Natural & Free-Form & Natural \\
2017 & SciQ [64] & Textual & Natural & Spans & Multi-choice \\
2017 & Qangaroo-MedHop [49] & Textual & Synthetic & Spans & Multi-choice \\
2017 & Qangaroo-WikiHop [49] & Textual & Synthetic & Spans & Multi-choice \\
2017 & TQA [31] & Multi-modal & Natural & Free-Form & Multi-choice \\
2017 & COMICS-Coherence [33] & Multi-modal & Natural & Free-Form & Multi-choice \\
2017 & COMICS-Cloze [33] & Multi-modal & Cloze & Free-Form & Multi-choice \\
2018 & QuAC [65] & Textual & Natural & Free-Form & Natural \\
2018 & CoQA [47] & Textual & Natural & Free-Form & Natural \\
2018 & SQuAD 2.0 [66] & Textual & Natural & Spans & Natural \\
2018 & HotpotQA-Distractor [67] & Textual & Natural & Spans & Natural \\
2018 & HotpotQA-Fullwiki [67] & Textual & Natural & Spans & Natural \\
2018 & DuoRC-Self [68] & Textual & Natural & Free-Form & Natural \\
2018 & DuoRC-Paraphrase [68] & Textual & Natural & Free-Form & Natural \\
2018 & CLOTH [69] & Textual & Cloze & Free-Form & Natural \\
2018 & ReCoRD [70] & Textual & Cloze & Free-Form & Natural \\
2018 & CliCR [71] & Textual & Cloze & Free-Form & Natural \\
2018 & ReviewQA [25] & Textual & Natural & Spans & Multi-choice \\
2018 & ARC-Challenge Set [72] & Textual & Natural & Free-Form & Multi-choice \\
2018 & ARC-Easy Set [72] & Textual & Natural & Free-Form & Multi-choice \\
2018 & OpenBookQA [73] & Textual & Natural & Free-Form & Multi-choice \\
2018 & SciTial [74] & Textual & Natural & Free-Form & Multi-choice \\
2018 & MultiRC [75] & Textual & Natural & Free-Form & Multi-choice \\
2018 & RecipeQA-Cloze [34] & Multi-modal & Cloze & Free-Form & Multi-choice \\
2018 & RecipeQA-Coherence [34] & Multi-modal & Natural & Free-Form & Multi-choice \\
2018 & PaperQA-Title [76] & Textual & Cloze & Free-Form & Multi-choice \\
2018 & PaperQA-Last [76] & Textual & Cloze & Free-Form & Multi-choice \\
2018 & PaperQA([PERSON] et al.) [77] & Textual & Natural & Spans & Natural \\
2018 & MCScript [78] & Textual & Natural & Free-Form & Multi-choice \\
2018 & ProPara [79] & Textual & Natural & Spans & Natural \\
2019 & Natural Questions-Short [80] & Textual & Natural & Spans & Natural \\
2019 & Natural Questions-Long [80] & Textual & Natural & Spans & Natural \\
2019 & DREAM [81] & Textual & Natural & Free-Form & Multi-choice \\
2019 & ShARC [38] & Textual & Natural & Free-Form & Multi-choice \\
2019 & CommonSenseQA [82] & Textual & Natural & Free-Form & Multi-choice \\
2019 & DROP [50] & Textual & Natural & Free-Form & Natural \\ \hline \hline \end{tabular}
\end{table}