Kaela wrote an equation, y = kx, to model the relationship between the circumference, y, and the diameter, x, of the circle. Which of the following statements correctly describe what k represents in this equation? k represents the unit rate
k represents the radius
k represents the constant of proportionality
k represents the area
A.
I, II, and IV only
B.
I and IV only
C.
I and III only
D.
II and III only