Answer:
b. y = 1000x
Constant of proportionality = 1,000
Explanation:
The equation that represents a proportional relationship between variable x and y usually takes the following form, y = kx.
Where,
k = constant of proportionality.
From the three given equations, the only equation that takes the form is b. y = 1000x.
The constant of proportionality (k) of the equation = 1,000.