用于表单的CSS网格系统(多列)

<form>
  <div class="row">
    <div class="col-md-6">
     <label for="input-first-name">First Name</label>
     <input type="text" id="input-first-name" name="first-name">
    </div>
    <div class="col-md-6">
     <label for="input-last-name">Last Name</label>
     <input type="text" id="input-last-name" name="last-name">
    </div>
  </div>
  <div class="row">
    <div class="col-md-12">
     <label for="input-email">Email</label>
     <input type="email" id="input-email" name="email">
    </div>
  </div>
  <div class="row">
    <div class="col-md-12">
     <button type="submit">Submit</button>
    </div>
  </div>
</form>