diff --git a/public/react/src/modules/courses/exercise/ExerciseDisplay.js b/public/react/src/modules/courses/exercise/ExerciseDisplay.js
index 4da4768d2..bd70bece6 100644
--- a/public/react/src/modules/courses/exercise/ExerciseDisplay.js
+++ b/public/react/src/modules/courses/exercise/ExerciseDisplay.js
@@ -120,35 +120,35 @@ class ExerciseDisplay extends Component{
               
               
                 return <SingleDisplay {...this.props} {...item} index={index} {...commonHandler}
-                    displayCount={exercise_questions.length} showActionButton={false}
+                    displayCount={exercise_questions.length} showActionButton={false} key={index}
                 ></SingleDisplay>
               
             } else if (item.question_type == 2) {
               
               
                 return <JudgeDisplay 
-                      showActionButton={false}
+                      showActionButton={false} key={index}
                       {...this.props} {...item} index={index} {...commonHandler} ></JudgeDisplay>
               
             } else if (item.question_type == 3) {
               
               
                 return <NullDisplay 
-                      showActionButton={false}
+                      showActionButton={false} key={index}
                       {...this.props} {...item} index={index} {...commonHandler} ></NullDisplay>
               
             } else if (item.question_type == 4) {
               
               
                 return <MainDisplay 
-                      showActionButton={false}
+                      showActionButton={false} key={index}
                       {...this.props} {...item} index={index} {...commonHandler} ></MainDisplay>
               
             } else if (item.question_type == 5) {
               
               
                 return <ShixunDisplay Testpapersettinghomepage
-                      showActionButton={false}
+                      showActionButton={false} key={index}
                       {...this.props} {...item} index={index} {...commonHandler} ></ShixunDisplay>
               
             }