This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
In a patient suffering from chronic myeloid leukemia, Hb falls from 11g% to 4g% in a short span of time, and splenomegaly occurs. The cause could be -a) Accelerated phaseb) CML in blast crisisc) Ineffective erythropoiesisd) Myelofibrosis 
Select and explain. 
A. ac, B. a, C. ab, D. bc
C: ab
Answer: C: ab 
Explanation: None