Answer:
C. Exchange the $100 bill for ten $10 bills.
Since the money is to be divided among 4 people, it is easier to divide it if the money is in equal denominations. Therefore, the first step should be to exchange the $100 bill for ten $10 bills, so that each person can receive an equal share of $25. This way, we can avoid having to deal with different denominations while dividing the money among the four people.