diff --git a/public/react/src/modules/courses/exercise/new/NullDisplay.js b/public/react/src/modules/courses/exercise/new/NullDisplay.js
index 079b1194f..b9bd893f9 100644
--- a/public/react/src/modules/courses/exercise/new/NullDisplay.js
+++ b/public/react/src/modules/courses/exercise/new/NullDisplay.js
@@ -103,14 +103,14 @@ class NullDisplay extends Component{
                         </div> */}
             <div className="options">
                 { 
-                    standard_answer.map((answers, index) => {
-                        return <div className="df answerRow" key={index}>
-                            <span className="lineh-40">答案（填空{index+1}）：</span>
+                    standard_answer.map((answers, _index) => {
+                        return <div className="df answerRow" key={_index}>
+                            <span className="lineh-40">答案（填空{_index+1}）：</span>
                             <div className="answers">
                                 { answers.answer_text.map((item, itemIndex) => {
                                     return <MarkdownToHtml 
                                         className="answer" key={itemIndex}
-                                        content={item} selector={'null_' + (index + 1) + '' + (itemIndex + 1)}     
+                                        content={item} selector={'null_' + (index + 1) + (_index + 1) + (itemIndex + 1)}     
                                     ></MarkdownToHtml>
                                 })}
                                 {/* <span className="answer" key={itemIndex}>{item}</span> */}