Myelosuppressive chemotherapy knocks down all marrow lineages, and when the platelet line is hit the patient needs a drug that pushes megakaryocytes back into production. Match each option to the lineage it supports. Erythropoietin and iron dextran both target the red cell pathway, so they fix anaemia, not low platelets. Tranexamic acid simply blocks clot breakdown to limit bleeding; it has no effect on marrow output. The only listed cytokine acting on the megakaryocyte-platelet axis is oprelvekin, the recombinant form of interleukin-11, which drives megakaryocytopoiesis and is licensed precisely for chemotherapy-related thrombocytopenia. By the lineage-matching logic, it is the answer.
\[\boxed{\text{Oprelvekin (interleukin-11)}}\]