select {
  font-family: "Helvetica Neue", sans-serif;
  font-size: 13px;
  font-weight: 600;
  width: 400px;
  transform-origin: bottom;
}

.my-dropdown-button {
  background-color: #f2f2f2;
  border: none;
  border-radius: 4px;
  padding: 12px 16px;
  box-shadow: 0 2px 4px 0 rgba(0, 0, 0, 0.2);
}

.container {
  display: flex;
  justify-content: center;
}

select option {
  position:relative;
}

select option:after {
  content:"___________________";
  position:absolute;
  bottom:-5px; /* adjust the position of the line */
  left:0;
  right:0;
  margin:0 auto;
  width:80%; /* adjust the width of the line */
  border-bottom:1px solid black; /* adjust the color and thickness of the line */
}

option {
  font-family: Arial, sans-serif;
  font-size: 16px;
  border-bottom: 1px solid #ccc;
  padding: 10px;
}