labour in vain

例句：

1. 1.The farmer spent all his time and effort on the farm, but it was all for nothing.
   这位农民在农场上花费了所有的时间和努力，但一切都是徒劳的。
2. 2.The teacher's hard work was in vain; the students didn't improve.
   老师的辛勤工作是徒劳的；学生们没有进步。
3. 3. Her efforts to save the environment were in vain; pollution still persisted.
   她为了拯救环境所做的努力都是徒劳的；污染仍然持续存在。