How to use ng-class in select with ng-options

<!doctype html>
<html ng-app="plunker">
  <head>
    <script src="http://code.jquery.com/jquery-1.9.1.min.js"></script>
    <script src="http://ajax.googleapis.com/ajax/libs/angularjs/1.0.5/angular.min.js"></script>
    <script src="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.0/js/bootstrap.min.js"></script>
    <script src="script.js"></script>
    <link href="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.0/css/bootstrap-combined.min.css" rel="stylesheet">
    <link rel="stylesheet" href="main.css" />
  </head>
  <body ng-controller="AppController">
    
    <select ng-model="Blah">
      <option ng-repeat="person in persons" ng-class="{red: person.Eligible}" ng-selected="{Blah == person.Name}">{{person.Name}}</option>  
    </select>

  </body>
</html>

.red {
  color: red;  
}

var app = angular.module('plunker', []);
app.controller('AppController',
    [
      '$scope',
      function($scope) {
        $scope.persons = [
          {Name:'John',Eligible:true},
          {Name:'Mark',Eligible:true},
          {Name:'Sam',Eligible:false},
          {Name:'Edward',Eligible:false},
          {Name:'Michael',Eligible:true}
        ];
        
        $scope.Blah = 'Sam';
        
      }
    ]
  );