Help improving code

Hey, I made the following code that checks the answers of a form:

<?PHP
include 'connect.php';
$points = 0;

foreach($_POST as $id => $answer){
$result = mysql_query("SELECT id, ans FROM questions WHERE id = '".$id."'");
$row = mysql_fetch_array($result);
    if($answer == $row['ans']) {
        $points++;
}
}
echo "Your score: $points";
?>

The problem is that it makes a sql query for every question, which makes the script a bit slow...

Is there a way to make a single sql query that select all the answers?