<div class="form-group">
  <% @exercise.pretty_choices.each do |choice| %>
    <div class="field">
      <%= form.radio_button(:content, choice.value, id: choice.id, required: true) %>
      <%= label_tag(choice.id, choice.text) %>
    </div>
  <% end %>
</div>

<div class="form-group">
  <% @exercise.pretty_choices.each do |choice| %>
    <div class="field">
      <%= form.radio_button(:content, choice.value, checked: checked(choice, @current_content), id: choice.id, required: true) %>
      <%= label_tag(choice.id, choice.text) %>
    </div>
  <% end %>
</div>

Add support for single choice
Add support for single choice
