code: public String getSelectedValue() {
          List<WebElement> options = getElement().findElements(By.tagName("option"));
          for (WebElement option : options) {
              if (option.isSelected()) {
                  return option.getAttribute("value");
              }
          }
          return null;
      }
docs: Get a single selected value. If multiple options are selected, then the first one is returned.
  
  @return A single selected value.