A 5-year-old child presents with history of fever off- and-on for past 2 weeks and petechial spots all over the body and increasing pallor for past 1 month. Examination reveals splenomegaly of 2 cm below costal margin. The most likely diagnosis is:
Acute leukemia Idiopathic thrombocytopenic purpura Hodgkin's lymphoma Aplastic anemia