Add multichoice question to quiz node programmatically
Finally, I got the solution. The below code is used to add the multichoice question node to quiz node.

  $multichoice_node = node_load($nid); //load multichoice question nid  
  $multichoice_node-&gt;add_directly = array(
    'latest' =&gt; array(
      $quiz-&gt;nid. '-'. $quiz-&gt;vid =&gt; $quiz-&gt;nid. '-'. $quiz-&gt;vid
    )
  );
  node_save($multichoice_node);