<form action="/test.php">
  <label for="douong">Chọn đồ uống:</label>
  <select name="douong" id="douong">
    <optgroup label="30k">
      <option value="cafe">Cà phê</option>
      <option value="nuoccam">Nước cam</option>
    </optgroup>
    <optgroup label="10k">
      <option value="trada">Trà đá</option>
      <option value="nuocloc">Nước lọc</option>
    </optgroup>
  </select>
  <br><br>
  <input type="submit" value="Xác nhận">
</form>

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