The correct answer to this open question is the following.
The person responsible for the discovery that stress leads to three distinct stages of physiological change: alarm reaction, resistance, and exhaustion was a scientist and doctor Hans Selye. He was the one who developed the theory called General Adaptation Syndrome or commonly known as GAS. The evidence was the result of his experiments and research made while working for the University of Mc Gill in Montreal, Canada. The experiment included rats in his laboratory that were put onto stressful situations. Dr. Slye observed the psychological changes in the animals.
