Which statement can you use to conclude that a relationship must be non-proportional?

The graph of the relationship is linear.
The graph of the relationship is linear.

The equation of the relationship is in the form y = kx
The equation of the relationship is in the form, y = kx

The relationship has a constant rate of change.
The relationship has a constant rate of change.

The y-intercept of the graph of the relationship is ( 0, 1).