Final answer:
The correct term for an organism that self-fertilizes and consistently produces offspring with identical traits is 'true-breeding,' which is also known as being homozygous. The correct option is d. True-breeding.
Step-by-step explanation:
If an organism, when allowed to self-fertilize, produces offspring with the same traits, it is called true-breeding.
True-breeding organisms are also referred to as homozygous, which means they have two identical alleles for a given trait. When such true-breeding individuals are crossed with others carrying different traits, such as black and white mice producing all gray offspring, this usually indicates an inheritance pattern of incomplete dominance, codominance or polygenic inheritance. True-breeding is a fundamental concept in Mendelian genetics, where alleles are passed on to the offspring resulting in a predictable phenotype if the organism is homozygous.
Therefore, the correct option is d. True-breeding.