Which is a major genetically modified crop in the united states?

The answer is; corn

Approximately 88 percent of all the corn in the United States is genetically modified. Most of these genetically modified corn is meant for animal feed. The other most genetically modified foods in the US are soy and cottonseeds.

good one: produce hormones that plants grow.

bad one: the problem with organic matter is that while plant nutrients are needed for crop growth, they can also stimulate excessive growth of the wrong plants – mainly, algae.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).