fix bug

app/templates/exercise_export/exercise_export.css

@@ -109,6 +109,9 @@ p{
     white-space: normal;
     min-height:12px;
 }
+.null-answer p{
+    display: inline-block;
+}
 .choose-radio{
     display: inline-block;
     width: 12px;

app/templates/exercise_export/exercise_user.html.erb

@@ -181,7 +181,7 @@
               <% if q_type ==  0 %>
                 <% q.exercise_choices.each do |s| %>
                   <% check_answer = (user_answer.present? && (s.id == user_answer.first.exercise_choice_id)) ? "choose-answer" : '' %>
-                  <div class="pbt5 clearfix main-choice">
+                  <div class="pbt10 clearfix main-choice">
                     <span class="choose-radio <%= check_answer %> pull-left mt8"></span>
                     <span class="inline-block pull-left ml10 choice-text"><%= to_markdown(s.choice_text,@request_url) %></span>
                   </div>
@@ -189,9 +189,9 @@
               <% elsif q_type == 1 %>
                 <% q.exercise_choices.each do |s| %>
                   <% check_answer = (user_answer.present? && (user_answer.pluck(:exercise_choice_id).include?(s.id))) ? true : false %>
-                  <div class="pbt5 clearfix main-choice">
+                  <div class="pbt10 clearfix main-choice">
                     <% if check_answer %>
-                      <span class="choose-checkbox choose-answer-multi mt8" ></span>
+                      <span class="choose-checkbox choose-answer-multi mt8 pull-left" ></span>
                     <% else %>
                       <span class="choose-checkbox pull-left mt8"></span>
                     <% end %>