I started training to be an accountant one year ago. I had more months to go and then I had to take exams.

A. By the time I've taken my exam, I will have started training to be an accountant for a year.

B. By the time I take my exam, I will have been in training to be an accountant for a year.

C. By the time I took my exam, I had been trained to be an accountant for a year.

D. By the time I've taken my exam, I will be training for a year.