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<select data-bind="options: currencies, value: selectedCurrency"></select>
<span data-bind="text: selectedCurrency"></span> selected!
function ViewModel() {
    var self = this;
    self.currencies = ko.observableArray(["USD", "GBP", "EUR", "JPY"]);
    self.selectedCurrency = ko.observable("USD");
}

ko.applyBindings(new ViewModel());