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
A child climbs with alternate steps, builds a tower 8–9 cubes, tells 'I' but not his name and can not say his age and sex, the probable age is – 
Select and explain. 
A. 36 months, B. 24 months, C. 30 months, D. 48 months
C: 30 months
Answer: C: 30 months 
Explanation: A child climbs stairs with alternating feet, refers to self as 'I' and builds a tower of 9 cubes by the age of 30 months.
A child knows his gender and age by 3 years.