Task: Question Answering
Input (English): The whole dataset consists of 81,826 samples annotated by native English speakers. 80% of them are used as training set. 10% of them are used as validation set while the rest is used as test set. 3000 hard samples are selected from the test set. 
 Question: What is the difference between the full test set and the hard test set?
Output (English): 3000 hard samples are selected from the test set