A proportional relationship has a proportionality constant (constant rate of change) and and must cross through the origin (or begin at (0,0). This means it's y-intercept is 0. Each of the options is a linear function. All of the functions have a constant rate of change. Only one as b=0 or 0 as the y-intercept.
B) y=4x has a constant of 4 and passes through the origin.
C) y=7x has a constant of 7 and passes through the origin.
