Answer:
A) Plants with genes for the toxin are eaten less often by insects, and therefore less insecticide is needed.
Step-by-step explanation:
Bt endoxin is lethal for some insects that ingest it (it is effective insecticide). Because of that, gene for the toxin is often used in the genetic engineering of certain plants, in order to reduce the use of pesticides. Unlike pesticides, which are unspecific (kill all insects, even those benefitial), Bt plants are a bit more specific.
Another advantage is that it has been shown that Bt corn is safe for human consumption.