block17.js

//App.js
// ...
import Posts from "./components/Posts"

function App() {
    return (
        <Router>
            <div>
                <nav style={{ margin: 10 }}>
                    <NavLink to='/' exact activeClassName='active'>
                        Home
                    </NavLink>
                    <NavLink to='/about' activeClassName='active'>
                        About
                    </NavLink>
                    <NavLink to='/posts' activeClassName='active'>
                        Posts
                    </NavLink>
                </nav>
                <Route path='/' exact component={Home} />
                <Route path='/about' component={About} />
                <Route path='/posts' component={Posts} />
            </div>
        </Router>
    )
}

export default App