<?php
add_filter( 'rwmb_meta_boxes', 'your_prefix_register_meta_boxes' );
function your_prefix_register_meta_boxes( $meta_boxes ) {
    $meta_boxes[] = array (
      'id' => 'question',
      'title' => 'Question',
      'pages' =>   array (
         'question',
      ),
      'context' => 'after_title',
      'priority' => 'high',
      'autosave' => false,
      'fields' =>   array (
        array (
          'id' => 'post_4',
          'type' => 'post',
          'name' => 'Post',
          'post_type' => 'post',
          'field_type' => 'select_advanced',
        ),

        array (
          'id' => 'textarea_bchoa_question_text',
          'type' => 'textarea',
          'name' => 'Question',
          'desc' => 'Please enter any additional content here - be as descriptive as you like.',
          'rows' => '3',
        ),

        array (
          'id' => 'checkbox_bchoa_notification',
          'name' => 'Notification',
          'type' => 'checkbox',
          'desc' => 'Check this box if you want to be notified of responses',
          'std' => 1,
        ),

        array (
          'id' => 'divider_3',
          'type' => 'divider',
          'name' => 'Divider',
        ),
      ),
      'validation' => [
        'rules' => [
          'post_title' => [
            'required'   => true,
            'minlength' => 5,
          ],
        ],
      ],
    );

    return $meta_boxes;
}