Answer:
Option B.
Explanation:
The constant of proportionality is the constant value of the ratio of two proportional quantities x and y; usually written y = kx, where k is the factor of proportionality.
Given that the graph is a straight line, we can find the constant of proporctionality just by selecting a point, and then dividing the y-value by the x-value.
We can see from the graph that when y=5, x=4. Then, the constant of proportionality comes to be:
k = 5/4 = 1.25.
Then, the correct option is Option B.