Nonlinear means that -- the graph isn't exactly the line. It's basically a "curve" like parabola.
Non-proportional means that --- the graph doesn't start from the origin point or doesn't start at (0,0).
( A ) is both linear and proportion.
( B ) is proportion BUT NOT LINEAR (It's curved.)
( C ) is linear and proportion.
( D ) Is linear BUT NOT PROPORTION (Doesn't start at (0,0) )
So ( B ) and ( D )
