Final answer:
Henry's behavior of not acknowledging his alcoholism represents the defense mechanism known as 'denial,' which is used to block awareness of painful or unsettling realities.
Step-by-step explanation:
When Henry states, "I don't know what you are talking about" in response to being called an alcoholic, he is exhibiting the defense mechanism known as denial. This defense mechanism involves refusing to accept reality or facts, thereby blocking external events from awareness. If a situation is too much for a person to handle, they may refuse to experience it as it might make them feel anxious or upset. Denial is a primary defense mechanism noted by Freud that is used by individuals to protect themselves from unpleasant realities through refusal to acknowledge them.