Over the past year, Lauren has repeatedly experienced symptoms that she believes indicate a heart attack, sending her to the emergency room complaining of dizziness, inability to catch her breath, and heart palpitations. She tells her parents she is afraid she's going to die, although doctors have found nothing physically wrong. From her symptoms, it is likely that Lauren is experiencing:

A) asthma attacks.
B) dissociative episodes.
C) manic episodes.
D) panic attacks.