Two Plants Are Crossed,resulting in Offspring with a 3:1 Ratio

Two plants are crossed,resulting in offspring with a 3:1 ratio for a particular trait.What does this suggest about the trait?

A) that the parents were true-breeding for contrasting traits
B) that the trait shows incomplete dominance
C) that a blending of traits has occurred
D) that the parents were both heterozygous for a single trait