diff --git a/public/react/src/modules/courses/exercise/question/single.js b/public/react/src/modules/courses/exercise/question/single.js
index 2edf8ab05..4ff4bf12b 100644
--- a/public/react/src/modules/courses/exercise/question/single.js
+++ b/public/react/src/modules/courses/exercise/question/single.js
@@ -41,7 +41,7 @@ class single extends Component{
         <Radio.Group disabled={ user_exercise_status == 1 ? true : false } defaultValue={questionType.user_answer[0]} onChange={this.changeItem}>
           {
             questionType.question_choices && questionType.question_choices.map((item,key)=>{
-              let prefix = isJudge ?  '' : `${tagArray[key]}.`
+              let prefix = isJudge ?  undefined : `${tagArray[key]}.`
               return(
                 <p className={parseInt(questionType.question_type) == 0 ? "clearfix mb15 df" : "fl mr40"}>
                   <Radio className="fl lineh-20" value={item.choice_id}>{prefix}</Radio>