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: Pediatrics
By what age a child can make tower of 3 cubes? 
Select and explain. 
A. 15 months, B. 18 months, C. 24 months, D. 28 months
B: 18 months
Answer: B: 18 months 
Explanation: 15 months - 2 cube tower
18 months - 3 cube tower
24 months - 6 cube tower
36 months - 9 cube tower