AngularJS Select绑定的是对象：

$scope.cars = { car01 : {brand : "Ford", model : "Mustang", color : "red"}, car02 : {brand : "Fiat", model : "500", color : "white"}, car03 : {brand : "Volvo", model : "XC90", color : "black"} };

<select ng-model="selectedCar" ng-options="y.brand for (x, y) in cars"></select>

现在想给select一个默认值怎么设置呢？