Update README.md

README.md

@@ -16,8 +16,8 @@ The codebase as well as the raw data can be found on [GitHub](https://github.com
 
 ### Data Fields
 
-- `source`: a `string` feature. Tells whether the question and answer is extracted from Parsebank, mC4-Fi or CC-Fi.
-- `id`: a `string` feature.
+- `source`: a `string` feature. Tells whether the question-answer pair is extracted from Parsebank, mC4-Fi or CC-Fi.
+- `id`: a `string` feature. Id of the original text from which the question-answer pair is extracted.
 - `question`: a `string` feature.
 - `answer`: a `string` feature. Can also be None (null).