The correct answer is A. Flower color is a recessive trait.
The recessive gene does not show its effect in heterozygous condition according to Mendel’s law of dominance. Thus, in heterozygous condition, dominant gene determines the phenotype for a trait. In this question a plant is homozygous for flower color. This indicates that pink flower determining gene can only be expressed in homozygous condition. Therefore, flower color is a recessive trait.
