We need to find the equation with a proportional constant of 0.25, so:
The option A has a constant of 25 ----> Incorrect.
The option B has a constant of 5/2 = 2.5 ---> Incorrect.
The option C has a constant of 1/4 = 0.25 ----> Correct.
The option D has a constant of 1/25 = 0.04 ----> Incorrect.
The option C is the correct answer.