Which of the following statements best describes how a corn plant comes to produce the Bt toxin?

AThe Bt gene is inserted into each plant cell, one at a time, by using a bacterial plasmid.

BThe bacteria containing the Bt gene are sprayed onto the corn plants.

CThe Bt gene is inserted into one plant cell by using a bacterial plasmid. D. The Bt gene is inserted into the soil and is taken into the corn plant through the roots.