Final answer:
The woman's enduring symptoms suggest Major Depressive Disorder, and antidepressants, combined with psychotherapy, would be appropriate treatments. Option a is the correct answer.
Step-by-step explanation:
The woman's symptoms, which include feelings of guilt, inability to sleep, concentrate, eat, or enjoy previous interests, could indicate several mental health conditions. Given the persistence and severity of her symptoms four months after her pet’s death, the most fitting diagnosis would be Major Depressive Disorder. This condition is characterized by deep sadness, sleeping and eating disturbances, lack of energy, and trouble concentrating, among other symptoms. Antidepressants and psychotherapy are common treatments. These may help adjust neurotransmitter levels and provide supportive coping mechanisms.
Adjustment Disorder may also be considered if symptoms are less severe and more directly linked to the specific event of losing her pet, in which case supportive therapy would be beneficial. PTSD and Generalized Anxiety Disorder don't appear to be the primary issues here, unless there's additional information about specific anxiety triggers or trauma-related symptoms directly linked to the event.