Here are the correct options for each blank:

6. The firm will be forced **D. making** concessions if it wants to avoid a strike.

12. His son was **A. enrolled** in military service a couple of years ago.

17. She tried to turn her dream **B. from** running her own business into reality.

18. You have to be aware **A. of** the damage humans are doing to quiken the extinction of wildlife.

19. Everyone I’ve talked to is in **C. subject** of the new dress code, so hopefully management will endorse it.

20. Many women had to pay a heavy **C. price** to win equality.

21. I try to set a good **A. cost** for my employees by always arriving to work on time and taking care of problems as they arise.

Feel free to ask if you need any further assistance!