The first stage in the Gas model of stress is alarm and mobilization. So the correct option in regards to the given question is option “d”. Hans Selye is the person that evolved this model and he has explained this model in complete details. He has broken down his model into three stages. The first stage involves alarm and mobilization. The second stage includes resistance. The third and the final stage include the exhaustion stage. These are the stages that an organism goes through to restore back the balance when stress is exerted from outside.