Answer:b- acute Stress Disorder
Step-by-step explanation: An Acute stress disorder is a mental disorder that follows a traumatic event either by direct experience as a witness or second hand experience gotten from listening to a traumatic event, usually one month after which can result to the victim to experience periods of anxiety and dissociation etc.
Here, Heather experiencing intense periods of anxiety and feels as if she is "in a daze" must have developed an Acute Stress Disorder as a result of listening to Matt's experiences.