fix bug

apps/exams/_static/js/public_exam_3g.js

@@ -59,10 +59,10 @@ $(function() {
         }
 
         if (limit > 0 && question_num >= limit) {
-            $(this).text('去支付');
+            $("#ex" + question_num + ' .next_question').text('去支付');
         }
 
-        console.log(limit, question_num,  $(this), typeof limit, typeof question_num);
+        console.log(limit, question_num);
 
 
         $(".answer-card").hide();