Form com BootStrap

<!DOCTYPE html>
<html lang="pt-br">
   <head>
      <meta charset="utf-8">
      <meta name="viewport" content="width=device-width, initial-scale=1">
      <title>Formulário de Cadastro</title>
      <!-- Adiciona o CSS do Bootstrap -->
      <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/css/bootstrap.min.css">
      <!-- Adiciona o jQuery e o JavaScript do Bootstrap -->
      <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
      <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.min.js"></script>
      <script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.5.2/js/bootstrap.min.js"></script>
   </head>
   <body>
      <nav class="navbar navbar-expand-lg navbar-light bg-light">
         <a class="navbar-brand" href="#">Formulário de Cadastro</a>
         <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav">
         <span class="navbar-toggler-icon"></span>
         </button>
         <div class="collapse navbar-collapse" id="navbarNav">
            <ul class="navbar-nav">
               <li class="nav-item active">
                  <a class="nav-link" href="#">Home</a>
               </li>
               <li class="nav-item">
                  <a class="nav-link" href="#">Listar Clientes</a>
               </li>
               <li class="nav-item">
                  <a class="nav-link" href="#">Novo Cliente</a>
               </li>
            </ul>
         </div>
      </nav>
      <div class="container mt-3">
         <form>
            <div class="form-group">
               <label for="nome">Nome:</label>
               <input type="text" class="form-control" id="nome" name="nome" required>
            </div>
            <div class="form-group">
               <label for="endereco">Endereço:</label>
               <input type="text" class="form-control" id="endereco" name="endereco" required>
            </div>
            <div class="form-row">
               <div class="form-group col-md-6">
                  <label for="cidade">Cidade:</label>
                  <input type="text" class="form-control" id="cidade" name="cidade" required>
               </div>
               <div class="form-group col-md-6">
                  <label for="estado">Estado:</label>
                  <select id="estado" name="estado" class="form-control" required>
                     <option value="" selected disabled>Selecione o Estado</option>
                     <option value="AC">Acre</option>
                     <option value="AL">Alagoas</option>
                     <option value="AP">Amapá</option>
                     <option value="AM">Amazonas</option>
                     <option value="BA">Bahia</option>
                     <option value="CE">Ceará</option>
                     <option value="DF">Distrito Federal</option>
                     <option value="ES">Espírito Santo</option>
                     <option value="GO">Goiás</option>
                     <option value="MA">Maranhão</option>
                     <option value="MT">Mato Grosso</option>
                     <option value="MS">Mato Grosso do Sul</option>
                     <option value="MG">Minas Gerais</option>
                     <option value="PA">Pará</option>
                     <option value="PB">Paraíba</option>
                     <option value="PR">Paraná</option>
                     <option value="PE">Pernambuco</option>
                     <option value="PI">Piauí</option>
                     <option value="RJ">Rio de Janeiro</option>
                     <option value="RN">Rio Grande do Norte</option>
                     <option value="RS">Rio Grande do Sul</option>
                     <option value="RO">Rondônia</option>
                     <option value="RR">Roraima</option>
                     <option value="SC">Santa Catarina</option>
                     <option value="SP">São Paulo</option>
                     <option value="SE">Sergipe</option>
                     <option value="TO">Tocantins</option>
                  </select>
               </div>
            </div>
            <button type="submit" class="btn btn-primary">Cadastrar</button>
         </form>
      </div>
   </body>
</html>