bootstrap form-control inside form does not work properly code example

Example 1: bootstrap form

<form>
  <div class="form-group">
    <label for="exampleInputEmail1">Email address</label>
    <input type="email" class="form-control" id="exampleInputEmail1" aria-describedby="emailHelp" placeholder="Enter email">
    <small id="emailHelp" class="form-text text-muted">We'll never share your email with anyone else.</small>
  </div>
  <div class="form-group">
    <label for="exampleInputPassword1">Password</label>
    <input type="password" class="form-control" id="exampleInputPassword1" placeholder="Password">
  </div>
  <div class="form-group form-check">
    <input type="checkbox" class="form-check-input" id="exampleCheck1">
    <label class="form-check-label" for="exampleCheck1">Check me out</label>
  </div>
  <button type="submit" class="btn btn-primary">Submit</button>
</form>

Example 2: 3 inputs in a row

<style>
    .tight-gutter {
        padding: 0 2px;
    }
</style>

<div class="row">
    <div class="col-sm-4 tight-gutter"><input type="text" class="form-control"></div>
    <div class="col-sm-4 tight-gutter"><select class="form-control"><option value="2">1</option></select></div>
    <div class="col-sm-4 tight-gutter"><input type="text" class="form-control"></div>
</div>