Answer:
(D). true-breeding.
Explanation:
True-breeding can be defined as a type of breeding, in which parents produce offspring with same phenotype as present in parents. In plants, true-breeding takes place only when their is self-fertilization.
These true-breeding organisms or varieties have a pure genotype (genetic makeup for a trait) and they show only a certain phenotype (physical expression of that trait).
Thus, the correct answer is option (D).