Answer:
The answer isn't D, it's C. I don't know why a verified answer is wrong, and I don't know how people are saying it's correct. I almost failed my test because of the "verified" answer above.
Step-by-step explanation:
1. Subtract 12,000 from 18,000 (6,000).
2. Since there are 12 months in each year and he's saving money each month for 4 years, multiply 12 and 4 (48).
3. Divide 6,000 by 48 (125).
Therefore, the answer is C. 125.