JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.aspnetcdn.com/ajax/knockout/knockout-3.0.0.js"></script>
 <!-- ko foreach: {data: answers, as: 'answer'} -->
  <li class="list-group-item">
    <input type="radio" 
           name="answers" 
      data-bind="checkedValue: answer, checked: $parent.response" />
    <span data-bind="text: answer.text"></span>
  </li>
 <!-- /ko -->

JavaScript

var vm = {
    answers: [
        { text: 'ans1' },
        { text: 'ans2' },
        { text: 'ans3' },
        { text: 'ans4' }
    ],
    response: ko.observable(answers[1])
};

vm.answer = vm.answers[1];

vm.response.subscribe(function(value) {
    console.log(value);
});

ko.applyBindings(vm);