It would be C
This is because..
A- 75 out of 100 boxes are filled
B- Represents 0.75 also known as 75%
C- Only has 8 boxes, 6 of which are filled in therefore showing that it is 60% of 80
D- is a replica to B but includes a bigger range of numbers, it still shows/represents 75%
Therefore, the answer is C