This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: DNB 2018, Subject name: Pediatrics
Child able to make tower of 5-6 cubes at which age? 
Select and explain. 
A. 18 months, B. 24 months, C. 21 months, D. 30 months
C: 21 months
Answer: C: 21 months 
Explanation: 15 months - Tower of 2 cubes 18 months - Tower of 4 cubes 21 months - Tower of 5-6 cubes 24 months - Tower of 6-7 cubes 3 years - Makes a BRIDGE of3 cubes 4 years - Makes a GATE of 5 cubes