Answer:
C
Step-by-step explanation:
Constant of proportionality is basically a ratio, or a unit rate.
For example, if there was the ratio 1:3, the COP (constant of proportionality) would be 3. If one pencil costs 50c, then the COP is .50 or 1/2.
In this problem, y is the single unit, and the COP is 0.25. That means that we need to find a unit rate that is multiplying by 0.25, or 1/4. This is found in option C.
