Select the option by the index, as determined by the "index" attribute of the
element.
public static void JsSelectByIndex(this OpenQA.Selenium.Support.UI.SelectElement selectElement, int index);
selectElement OpenQA.Selenium.Support.UI.SelectElement
This OpenQA.Selenium.Support.UI.SelectElement.
index System.Int32
The value of the index attribute of the option to be selected.