Normál lenyíló

<div class="form-group ">
    <label for="selectCountries" class="control-label ">Normál lenyíló</label>
    <select class="form-control" id="selectCountries" aria-label="Leíró szöveg">
        <option>option 1</option>
        <option>option 2</option>
        <option>option 3</option>
        <option>option 4</option>
    </select>
</div>

.form-group {
     margin-bottom: 25px;
}
 .control-label, label {
     text-transform: uppercase;
     font-weight: 400;
     font-size: 1rem;
}
 select.form-control {
     height: auto;
     color:#000;
}

Lenyíló, súgóval

<div class="form-group">
    <div class="relative clearfix">
        <label for="letoltIg" class="control-label">label</label>
        <a data-placement="top" tabindex="0" class="help pull-right" role="button" data-toggle="popover" data-trigger="focus" data-content="And here's some amazing content. It's very engaging. Right?" data-original-title="Popup címe" aria-label="Leíró szöveg"><i class="far fa-question-circle" aria-hidden="true"></i></a>
    </div>

    <div class="row">
        <div class="col-lg-12 col-md-12">
            <select class="form-control" id="letoltIg" aria-label="Leíró szöveg">
                <option>option 1</option>
                <option>option 2</option>
                <option>option 3</option>
                <option>option 4</option>
            </select>
        </div>
    </div>
</div>

.form-group {
	margin-bottom: 25px;
}
.relative {
	position: relative;
}
.control-label,
label {
	text-transform: uppercase;
	font-weight: 400;
	font-size: 1rem;
}
main a.help {
	display: inline-block;
	font-size: 1rem;
}
main a {
	color: #004b88;
	font-weight: 700;
	border-bottom: 1px solid transparent;
	padding: 0;
	-webkit-transition: color 0.5s ease-out, border-bottom 0.5s ease-out;
	transition: color 0.5s ease-out, border-bottom 0.5s ease-out;
	cursor: pointer;
}
select.form-control {
	color: #000;
	height: auto;
}
select.form-control option:checked,
select[multiple]:focus option:checked,
select.form-control option:hover,
select[multiple]:focus option:hover {
	background-color: #004b88 !important;
	color: #fff !important;
}