Promoter 2 is the best choice because the resistance gene will only be expressed in the leaves of the corn plant. Promoter 3 only expresses genes in the corn roots, so the toxin would not be available in the leaves for the pest to eat. Promoters 1 and 4 would express the resistance gene in the leaves of the corn plant, but the toxins would be expressed in the corn cobs as well, which may then be fed to livestock.
