How Was "Genetic Engineering" Used in the Development of Modern

How was "genetic engineering" used in the development of modern corn from its relative teosinte?

A) People harvesting the teosinte selected the plants with more desirable traits and so those genes spread in the population, eventually resulting in modern corn.
B) People got tired of harvesting the teosinte as it was, so they cross pollinated it with other plants with seeds on cobs, and wound up with modern corn
C) People selected the genes which controlled cob and kernel size in teosinte and inserted them into related plants, eventually developing modern corn
D) People harvesting corn plants selected desirable traits and ended up with modern, large cob teosinte, now known as modern corn
E) Scientists have found five genes which control the differences between teosinte and modern corn, but cannot determine how they were engineered from one to the other