Adding class to cakephp checkbox input instead of div

I'm trying to put the

class="answer_class"

inside all of my checkboxes, however it is creating a div instead and placing the checkboxes there. What should I alter in my code to do what I intend?

          $question['question_id'] => array(
            'type'=>'select',
            'multiple'=>'checkbox',
            'options'=> $answers,
            'class'=> 'answer_class',                    
            'label' => false
          )