Answer: Denial Stage
Explanation: According to Elizabeth Kübler-Ross’s stages of grief model, there are five stages of grief and they are: Denial, Anger, Bargaining, Depression and Acceptance.
Each of the stage has it's part to play in grief model.
According to the question, Jack was on the Denial stage. On hearing others talking about the terrorist attack on New York City, He was surprised and could not imagine what it would be like for New York City to be attacked. He could not bring himself to accepting that his city will be attacked and how will he cope with the whole situation.