The amount of water in a bathtub that is getting filled at a constant rate is shown in the the table below.

To find the missing value in the table, we can first determine the rate of water being added to the bathtub by analyzing the amounts given in the table.

We can look at the differences in amounts of water at the provided times:

1. From 3 seconds (375 mL) to 7 seconds (875 mL):
- 875 mL - 375 mL = 500 mL
- Time difference = 7 seconds - 3 seconds = 4 seconds
- Rate = 500 mL / 4 seconds = 125 mL/second

2. From 7 seconds (875 mL) to 9 seconds (1,125 mL):
- 1,125 mL - 875 mL = 250 mL
- Time difference = 9 seconds - 7 seconds = 2 seconds
- Rate = 250 mL / 2 seconds = 125 mL/second

3. From 9 seconds (1,125 mL) to 12 seconds:
- We need to find the amount at 12 seconds.
- Time difference = 12 seconds - 9 seconds = 3 seconds
- Amount added = 125 mL/second * 3 seconds = 375 mL

Thus, the amount of water at 12 seconds will be:
1,125 mL + 375 mL = 1,500 mL.

4. We can also confirm this with the last known amount:
- From 12 seconds to 17 seconds:
- Time difference = 17 seconds - 12 seconds = 5 seconds
- Amount added = 125 mL/second * 5 seconds = 625 mL
- Amount at 17 seconds = 1,500 mL + 625 mL = 2,125 mL, which checks out.

Therefore, the missing value in the table is:

C. 1,500 milliliters.