bootstrap select box arrow not visible

1// bootstrap select box arrow not visible
2// Solution - Add form-select class next to the form-control class 
3// for B5 Version
4
5<select class="form-control form-select">
6    <option>Select Title</option>
7    <option value="1">Title 1</option>
8    <option value="2">Title 2</option>
9</select>