She did not have enough nurses to cover for those who went ill or took holiday.她没有足够的护士来顶替那些生病或休假的人工作。Review all the notes you need to cover for each course.把每一门课程需要掌握的笔记都复习一下。She'll be out for a week, so the rest of us will have to cover for her.她要离开一个星期，这样我们大家就得替她的班。