Recently,beekeepers Have Noticed an Alarming and Sudden Disappearance of Honeybees

Recently,beekeepers have noticed an alarming and sudden disappearance of honeybees from their hives.Some beekeepers and environmentalists worry that crops genetically engineered to produce Bt insecticidal toxin may be killing the bees.Which of these experiments tests the hypothesis that Bt toxin is killing the bees?

A) spraying Bt toxin on a field and counting the number of bees present before and after spraying
B) collecting hundreds of bees; half of the bees would be kept in a facility with plants genetically engineered to contain the gene for Bt toxin, while the other half would be kept in a facility with plants not genetically engineered to contain the gene for Bt toxin. The survival rate for both sets of bees would be calculated and compared.
C) collecting hundreds of bees and spraying only half of them with Bt toxin; the survival rate for both sets of bees would be calculated and compared
D) The number of bees in two adjacent fields would be counted before and after spraying one of the fields with Bt toxin. The survival rate of bees in both fields would be calculated and compared.