In this scenario, Jack is most likely practicing the act of mindfulness.
Mindfulness refers to the act of maintaining a present awareness of the thoughts, feelings and surrounding environment.
The act of Mindfulness is a relaxation technique that help to live in the moment and ignore thoughts of both past and future.
Therefore, the Option A is correct because Jack is definitely practicing the act of mindfulness to help live in the moment and ignore thoughts of both past and future.
The missing options includes "a) mindfulness b) tai chi c) biofeedback d) autohypnosis"
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