question: In what year did a research study find that the use of Bt toxin plants failed to be effective after 7 years ?
answer: 2006
turker_answer: A research study found in 2006 that the use of Bt toxin plants failed to be effective after 7 years .
rule-based: Did a research study find that the use of Bt toxin plants failed to be effective after 7 years in 2006 .