<form>
    <fieldset>
        <legend>Оберіть улюблене чудовисько</legend>

        <input type="radio" id="mavka" name="monster" value="M" />
        <label for="mavka">Мавка</label><br />

        <input type="radio" id="vovkulaka" name="monster" value="V" />
        <label for="vovkulaka">Вовкулака</label><br />

        <input type="radio" id="potercha" name="monster" value="P" />
        <label for="potercha">Потерча</label>
    </fieldset>
</form>

legend {
    background-color: #000;
    color: #fff;
    padding: 3px 6px;
}

input {
    margin: 0.4rem;
}