bootstrap form input dropdown
snippet in html

bootstrap input

user7061

<div class="form-group">
    <label for="input">Form Input</label>
    <input class="form-control" type="text" id="input" name="inputName" placeholder="Place holder" value="" autocomplete="on" />
</div>

bootstrap select input

user1499

<div class="form-group">
    <label for="exampleFormControlSelect1">Example select</label>
    <select class="form-control" id="exampleFormControlSelect1">
      <option>1</option>
      <option>2</option>
      <option>3</option>
      <option>4</option>
      <option>5</option>
    </select>
  </div>
  <div class="form-group">
    <label for="exampleFormControlSelect2">Example multiple select</label>
    <select multiple class="form-control" id="exampleFormControlSelect2">
      <option>1</option>
      <option>2</option>
      <option>3</option>
      <option>4</option>
      <option>5</option>
    </select>
  </div>

bootstrap form input dropdown

user5259

<div class="col-lg-6 col-md-6 col-12">
  <div class="input-group mb-3">
    <div class="input-group-prepend">
      <select class="form-control select2bs4" name="country_code" id="country_code" style="width: 100%">
        <option value="+91">+91</option>
        <option value="+351">+351</option>
        <option value="+1">+1</option>
      </select>
    </div>
    	<input type="text" name="user" class="form-control" placeholder="Email Or Mobile Number">
    </div>
</div>