Translations:Optional settings/129/en

You can also add .html after the survey id in the following way:

       // Use short URL
		'urlManager' => array(
			'urlFormat' => 'path',
			'rules' => array (
			    '<sid:\d+>' => array('survey/index','urlSuffix'=>'.html','matchValue'=>true),
			 ),
			'showScriptName' => false,
		),

For more information, check the Yii documentation.