fail to keep up落後;跟不上John fell behind in his studies and finally had to leave school. 約翰學習跟不上,最後只好退學。
To be promoted or to fall behind is not a matter of salary but even more a matter of selfrespect. 升職或者落後不僅僅是薪金的問題,更重要的是自尊。
I don't want to fall behind in my studies. 在學習上我不想落伍。
Diligence helps one to go forward,where as laziness makes one fall behind. 勤奮使人上進,懶惰使人落後。