keep track of

「track」是「行蹤、軌跡」，「keep track of」則是掌握行蹤、軌跡，例如：

It's hard to keep track of time in this playground.（在這個遊樂場裡，很容易忘了時間。）

The professor wishes to keep track of your progress.（那位教授希望隨時掌握你的進度。）

To keep track of the time, she marked off the days on her calendar.（為了算日子，她每天都在日曆上做記號。）

bent on

「bent on」的意思是「一心一意、下定決心」，例如：

Margaret seems bent on becoming an actress. （瑪格麗特似已決意要當演員。）

Beckham is bent on winning at all costs.（貝克漢決心不惜一切去爭取勝利。）

They are always bent on interfering in other countries’ internal affairs.（他們總是蓄意干涉別國內政。）