66. A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the triazine works well and almostall the pigweed dies; but after several years, the farmer sees more and more pigweed. Which of these explanations bestexplains what happened?
(A) The herbicide company lost its triazine formula and started selling poor-quality triazine.
(B) Triazine-resistant pigweed has less-efficient photosynthesis metabolism.
(C) Natural selection caused the pigweed to mutate, creating a new triazine-resistant species.
(D) Triazine-resistant weeds were more likely to survive and reproduce.
(E) Disruptive selection caused the pigweed to produce a new triazine-resistant species.