If I had worked a little bit harder in college, I could have became a much better writer, and maybe that would have led me to getting a better job in my field. Let that be a lesson to young students - work hard, study hard, and focus on the end goal
IMO answer is C
(A) If I had worked a little bit harder in college, I could have became a much better writer, and maybe that would have led me to getting a better job in my field. Let that be a lesson to young students - work hard, study hard, and focus on the end goal ->
became is V2, we should use V3, so incorrect
(B) If I worked a little bit harder in college, I could become a much better writer, and maybe that would lead me to getting a better job in my field. Let that be a lesson to young students -
work hard, study hard, and focus on the end goal - this is not subjunctive mood(C) If I had worked a little bit harder in college, I could have become a much better writer, and maybe that would have led me to getting a better job in my field. Let that be a lesson to young students - work hard, study hard, and focus on the end goal -
Correct proper subjunctive mood(D) If I work a little bit harder in college, I could have become a much better writer, and maybe that would have led me to getting a better job in my field. Let that be a lesson to young students - work hard, study hard, and focus on the end goal.
Incorrect subjunctive mood(E) If I had worked a little bit harder in college, I will become a much better writer, and maybe that will lead me to getting a better job in my field. Let that be a lesson to young students - work hard, study hard, and focus on the end goal -
With had, we have to write could have