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Form Bootstrap 4

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<form>
	<div class="form-group">
		<label for=""></label>
		<input type="text" class="form-control" id="" aria-describedby="" placeholder="">
	</div>
	<div class="form-group">
		<label for=""></label>
		<input type="text" class="form-control" id="" aria-describedby="" placeholder="">
	</div>
	<button type="submit" class="btn btn-primary">Submit</button>
</form>

bootstrap 4 form inline

<form class="form-inline py-3">
  <input type="text" class="form-control"/>
  <input type="text" class="form-control"/>
  <button type="submit" class="btn btn-primary">Submit</button>
</form>

form bootstrap 4

<form>
  <div class="form-row align-items-center">
    <div class="col-auto">
      <label class="sr-only" for="inlineFormInput">Name</label>
      <input type="text" class="form-control mb-2" id="inlineFormInput" placeholder="Jane Doe">
    </div>
    <div class="col-auto">
      <label class="sr-only" for="inlineFormInputGroup">Username</label>
      <div class="input-group mb-2">
        <div class="input-group-prepend">
          <div class="input-group-text">@</div>
        </div>
        <input type="text" class="form-control" id="inlineFormInputGroup" placeholder="Username">
      </div>
    </div>
    <div class="col-auto">
      <div class="form-check mb-2">
        <input class="form-check-input" type="checkbox" id="autoSizingCheck">
        <label class="form-check-label" for="autoSizingCheck">
          Remember me
        </label>
      </div>
    </div>
    <div class="col-auto">
      <button type="submit" class="btn btn-primary mb-2">Submit</button>
    </div>
  </div>
</form>