英语翻译Write an event handler on the unordered list for the hov

英语翻译Write an event handler on the unordered list for the hover event so that when you user hovers over the list,all the even countries will have the "red,boldface" style applied.(By even countries,I mean United Kingdom,Spain,Czech Republic.) You can put a class attribute on every second list item to facilitate this.求解释HOVER OVER指的是什么?