Which statement describes true-breeding plants?

True-breeding plants are those that, when self-fertilized or crossed with another true-breeding plant of the same variety, produce offspring that consistently exhibit the same characteristics or traits as the parent plants. This consistency occurs because true-breeding plants are homozygous for the traits in question, meaning they have two identical alleles for a given gene.

When these plants reproduce, whether through self-pollination or controlled cross-pollination with another true-breeding plant, the offspring inherit the same alleles, leading to uniformity in traits such as color, height, or flower shape. This predictability is crucial in genetics, agriculture, and breeding programs, as it allows breeders to maintain desired traits in successive generations of plants.

The other choices suggest variability or dependence on external factors. For instance, plants producing variable traits or requiring crossbreeding contradict the essence of true-breeding, which is defined by its reliability in producing uniform offspring. Similarly, referencing genetically modified organisms does not pertain to the fundamental concept of true-breeding as it involves human intervention to alter genetic materials rather than relying on natural breeding.