Final answer:
The test that is most useful in differentiating Fanconi anemia from other causes of pancytopenia is Diepoxybutane-induced chromosome breakage (c).
Step-by-step explanation:
The test that is most useful in differentiating Fanconi anemia from other causes of pancytopenia is Diepoxybutane-induced chromosome breakage (c). Fanconi anemia is a genetic disorder that affects the bone marrow's ability to produce blood cells. Diepoxybutane-induced chromosome breakage test measures the sensitivity of patient's cells to a chemical that produces DNA damage, which is a characteristic feature of Fanconi anemia.