bootstrap4.css
.d-inline-flex {
  display: -ms-inline-flexbox !important;
  display: inline-flex !important;
}
bootstrap4.css
@media (min-width: 768px) {
  .d-md-none {
    display: none !important;
  }
  .d-md-inline {
    display: inline !important;
  }
  .d-md-inline-block {
    display: inline-block !important;
  }
  .d-md-block {
    display: block !important;
  }
  .d-md-table {
    display: table !important;
  }
  .d-md-table-row {
    display: table-row !important;
  }
  .d-md-table-cell {
    display: table-cell !important;
  }
  .d-md-flex {
    display: -ms-flexbox !important;
    display: flex !important;
  }
  .d-md-inline-flex {
    display: -ms-inline-flexbox !important;
    display: inline-flex !important;
  }
}