What Did the Scientists Conclude from Figure 4

What did the scientists conclude from figure 4.24?

A) The fewer copies of a defective CFTR gene an organism has, the more resistant it is to cholera toxin
B) The number of defective CFTR genes did not correlate with resistance to cholera toxin
C) The more cholera toxin an organism was exposed to, the more copies of its CFTR gene that became defective
D) The more cholera toxin an organism was exposed to, fewer copies of its CFTR gene that became defective
E) The more copies of a defective CFTR gene an organism has, the more resistant it is to cholera toxin