A middle-aged female patient presents to the clinic with fatigue, pallor, and easy bruising. Her blood tests show pancytopenia with low counts of red cells, white cells, and platelets. A bone marrow biopsy is performed, revealing a predominance of empty, fatty marrow spaces with significantly reduced blood-forming cells. There is no evidence of malignant cells or fibrosis. The patient does not have a history of exposure to toxic chemicals, and there is no family history of similar conditions. Based on the clinical scenario and bone marrow findings, what is the most likely diagnosis?
a. Myelofibrosis
b. Polycythemia vera
c. Acute myeloid leukemia
d. Aplastic anemia