为什么＆＃39; react-router-dom＆＃39;显示＆＃39;无法获得＆＃39;

Question

我创建了简单的网络应用程序并尝试连接react-router-dom，当我启动应用程序时，它显示了组件Audience（网址：localhost:3000） ，但如果我将网址更改为localhost:3000/board或localhost:3000/speaker，则会显示Cannot GET /board或Cannot GET /speaker

＆＃13;

＆＃13;

import React from 'react';
import ReactDOM from 'react-dom';
import { BrowserRouter as Router, Route, Link } from 'react-router-dom'

import Audience from './components/Audience.jsx';
import Board from './components/Board.jsx';
import Speaker from './components/Speaker.jsx';

ReactDOM.render(
<Router>
  <div>
    <Route path="/" component={Audience}/>
    <Route path="/board" component={Board}/>
    <Route path="/speaker" component={Speaker}/>
  </div>
</Router>, document.getElementById('root'))

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>

<div id="root"><div>

＆＃13;

＆＃13;

＆＃13;