diff --git a/public/react/src/modules/courses/exercise/new/SingleDisplay.js b/public/react/src/modules/courses/exercise/new/SingleDisplay.js
index 4018fcbbe..b7a1905fc 100644
--- a/public/react/src/modules/courses/exercise/new/SingleDisplay.js
+++ b/public/react/src/modules/courses/exercise/new/SingleDisplay.js
@@ -92,7 +92,7 @@ class SingleDisplay extends Component{
             {/* 单选 or 多选 */}
             <div className="options">
                 { question_choices.map((item, optionIndex) => {
-                  let prefix = ''
+                  let prefix = undefined
                   if (!isPreviewPage) {
                     prefix = `${tagArray[optionIndex]}.`
                   }