Update app.py

app.py

@@ -70,7 +70,7 @@ def process_and_grade(file_path, non_question_columns_str):
 def grade_answer(question, participant_answer, key_answer):
     question = str(question)
     participant_answer = str(participant_answer)
-    key_answer = str(participant_answer)
+    key_answer = str(key_answer)
     """
     Call the fine-tuned model to grade an answer based on the question,
     the participant's answer, and the key answer.