The answer is a because if u do a punnett square to get your results like i did, each plant would end up with the phenotype Y(yellow)y(green), and since they all have 1 dominant and 1 recessive, the dominant trait takes over, but the recessive trait is still there but it doesnt show up.
hopefully my answer helps u
I guess because its not exactly a smooth surface therefore creating friction in other words itsa rough surface
