Question: What does "double knock" in weed control mean? Need Assignment Help? Select one: a. Using a second, different Mode of Action group herbicide to kill any weed survivors from the first herbicide application. b. Using a grass weed herbicide followed closely by a broadleaf weed herbicide. c. Using a second, same Mode of Action group herbicide to kill any weed survivors from the first herbicide application. d. Using two applications of the same herbicide, with the second application at a higher rate to kill any weed survivors from the first application.