When a Farmer Grows Cotton Containing the Gene for Bt

When a farmer grows cotton containing the gene for Bt toxin,they often leave a strip of non-Bt cotton around the outside of the field (Figure 10.27) for what reason?

A) To allow some rr bollworm caterpillars to survive
B) Because the non-Bt cotton grows better
C) To allow some RR bollworm caterpillars to survive
D) Because the non-Bt cotton does not drive the moths and caterpillars to extinction
E) To allow the non-Bt and Bt cotton plants to cross pollinate