fix bug

Author: wjj0122

Diff for: README.md

@@ -57,6 +57,8 @@ wget https://dl.fbaipublicfiles.com/contriever/embeddings/contriever-msmarco/wik
 cd parser
 python parse_result.py
 ```
+### 4.Evaluation
+The evaluation code of each dataset can be found in `parser/qa_eval.ipynb`. Please fill in the path of parse result file(a `.csv` file) and corresponding qa data file(like `../fine-tuning/data/2wikimqa_500.json`) in `qa_eval.ipynb` to run correctly.
 
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