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?

hover over指的是鼠标悬停在某控件之上.
为无序列表写一个悬停事件的事件处理程序,使得用户鼠标悬停在列表上时,所有的双数国家会使用“红色,粗体”格式（我所指的双数国家是...）.为方便起见,你可以在每个双数列表项上使用一个类属性.