This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Haematology, Subject name: Pathology
Which of the following statements is true 
Select and explain. 
A. Chronic myeloid leukemia occurs beyond 50 years of age, B. Hairy cell leukemia in less than 50 years has a good prognosis, C. Acute lymphoid leukemia in less than 1 year has a poor prognosis, D. Chronic lymphocytic leukemia occurs in less than 50 years of age
C: Acute lymphoid leukemia in less than 1 year has a poor prognosis
Answer: C: Acute lymphoid leukemia in less than 1 year has a poor prognosis 
Explanation: There are 4 main types of leukemia, based on whether they are acute or chronic, and myeloid or lymphocytic: Acute myeloid (or myelogenous) leukemia(AML) Chronic myeloid (or myelogenous) leukemia(CML) Acute lymphocytic (or lymphoblastic) leukemia (ALL) Chronic lymphocytic leukemia (CLL)