Why might you find two kanamycin resistance genes on different parts of a T-DNA plasmid?

A. One of the genes could be used for positive selection, and one could be used for negative selection

B. One of the genes could be used for selection in plants, and one could be used for selection in bacteria

C. This arrangement facilitates site-specific recombination for marker-free selection

D. Each gene might have been introduced by a independent co-transformation event

Answer: Option B