Answer:
Corn crop is resistant to herbicides because they are genetically modified through genetic engineering. There are some bacteria which are resistant to herbicides i. e. no effect of chemicals on that bacteria. So the biotechnologist take a gene from this resistant bacteria and induced it in the corn plant which becomes the part of their genetic makeup. So when we apply herbicide, the gene produces some enzymes which cancel the adverse affect of herbicide and only weeds are affected.
Dinosaurs became common on land