A Farmer Uses Triazine Herbicide to Control Pigweed in His

Multiple Choice

A farmer uses triazine herbicide to control pigweed in his field.For the first few years,the triazine works well and almost all the pigweed dies;but after several years,the farmer sees more and more pigweed.Which of these explanations best describes this observation?

A) The herbicide company lost its triazine formula and started selling poor-quality triazine.
B) Natural selection caused the pigweed to mutate,creating a new triazine-resistant species.
C) Triazine-resistant pigweed has less-efficient photosynthesis metabolism.
D) Only triazine-resistant weeds survived and reproduced,so each year more pigweed was triazine-resistant.