to achive this task we only need to paste the code given below in your list.phtml file

$productSku= $_product->getSku();
$product= Mage::getModel('catalog/product');
$productId= $product->getIdBySku($productSku);
 
$product= Mage::getModel("catalog/product")->load($productId);
 
$attVal= $product->getOptions();
 
$optStr= "";
 
// loop through the options
foreach($attValas $optionKey => $optionVal) {
 
//$optStr .= "<br/>";
 
//$optStr .= $optionVal->getTitle().": ";
 
$optStr.= "<select style='display:block; clear:both;' name='options[".$optionVal->getId()."]'>";
 
foreach($optionVal->getValues()as$valuesKey => $valuesVal) {
$optStr.= "<option value='".$valuesVal->getId()."'>".$valuesVal->getTitle()."</option>";
}
 
$optStr.= "</select>";
 
}
 
echo($optStr);