答案可能不唯一,比如我们可以说：Lessons finish / end / are over at half past four in the afternoon.= 课程下午四点半结束；
也可以说：Lessons begin / start at half past four in the afternoon = 课程下午四点半开始；
甚至还可以说：Lessons are giving at half past four in the afternoon = 下午四点半正在上课.