angularjsでselect assign ng-options構成メソッドを使用するにはどうすればよいですか?

$scope.years = [2014, 2015, 2016];

 <select ng-model="item" ng-options="item as y for y in years">
 </select>

$scope.item = 2016;
$scope.years = [2014, 2015, 2016];

$scope.sites = [
 {site : "baidu", url : "https://www.baidu.com"},
 {site : "163", url : "http://www.163.com"},
 {site : "sina", url : "http://www.sina.com"}
];

 <select ng-model="s.site" ng-options="s.site as s.site group by site.group for s in sites">
 </select>

$scope.site = "163";
$scope.sites = [
 {site : "baidu", url : "https://www.baidu.com"},
 {site : "163", url : "http://www.163.com"},
 {site : "sina", url : "http://www.sina.com"}
];

$scope.cars = {
car1 : {brand : "BYD", model : "Y50", color : "red"},
car2 : {brand : "CC", model : "HF", color : "white"},
car3 : {brand : "JL", model : "JL10D", color : "black"}
};

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

$scope.site = "BYD";
$scope.cars = {
car1 : {brand : "BYD", model : "Y50", color : "red"},
car2 : {brand : "CC", model : "HF", color : "white"},
car3 : {brand : "JL", model : "JL10D", color : "black"}
};

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