Susan trained her rat to press a bar in a skinner box in order to get a food pellet. susan's rat pressed the bar a lot. however, later when susan ran out of food pellets, her rat eventually stopped pressing the bar. what had happened?

what have scientists found to be the most efficient and effective way to insert new sequences into an individual? a-scientists have created genetically altered foods that release dna during digestion. b-scientists use viruses to insert specific gene sequences. c-scientists irradiate genes so that they can be absorbed through the skin.