I think it is C, because if I'm right present principal is something that is happening presently? If so, C would be the answer because they "are doing" the exercises right now in context.
Answer:
These
Explanation:
It is a determined that is it is a demonstrative adjective that helps provide specification on the information.
1. Who
2. Whom
3. Whom
4. Who
5. Whom
6. Who
7. Who
8. Whom
9. Who
10. Whom
11. Who
12. Who
13. Who
14. Who
15. Whom
16. Who
17. Whom
18. Who
19. Who
20. Who
21. Who
