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: Anatomy
Examination of a peripheral smear demonstrates leukemia composed of small mature lymphocytes without blast forms.which of the following is most likely age of this patient? 
Select and explain. 
A. 1year, B. 20 years, C. 45years, D. 65years
D: 65years
Answer: D: 65years 
Explanation: Different leukemias tend to affect populations of different ages. The disease described is chronic lymphocytic leukemia which is a disease of older adults.(ref Robbins 8th/604, 9/e p593)