Science suggests that the gene that regulates cystic fibrosis TRs or CFTRs evolved in northern European populations:

A) due to their close proximity to livestock animals.
B) as part of a balanced polymorphism that protected the majority against death by cholera.
C) following their regression back to foraging from farming.
D) as an adaptive response to smallpox.
E) None of the answers is right, because it was first seen in people of Canadian, French, Tanzanian, and Romanian descent.