The effectiveness of BT-Corn compared to conventional insecticide treatment is very much higher:
* The plant itself produces the toxin that blocks the digestion of or target insects: the entire plant is protected where a treatment (out of neonicotinoids, very expensive and reserved to the seed treatment) allows only a protection of surface and must be renewed several times.
* The selectivity of the treatment is very superior: each variant of the BT molecule targets only a family of insects but we do not know the impact of their cumulative effects in the environment.
I think it is A but not 100% sure. Think of an enzyme like a key unlock the lock is the protein. And to activate getting inside your car or house you have to fit the key into the lock.
