Final answer:
Without additional context, there is insufficient information to determine if the proportionality constant of 4/3 applies to all relationships between y and x for line a, although in direct proportionality situations, y = (4/3)x would be true.
Step-by-step explanation:
Given that the constant of proportionality between y and x for line a is 4/3, this implies a linear relationship where y is directly proportional to x. This means any equation that represents line a would take the form y = kx, where k is the constant of proportionality. In this case, k is 4/3. Therefore, if this is the complete information provided and the line has no y-intercept, which is not mentioned, the statement True would be correct, as it would mean the equation would be y = (4/3)x. However, without the context that the line passes through the origin (which would exclude any y-intercept), there's insufficient information to determine whether this statement is true about any and all relationships between y and x.