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: Dental
According to piagets, the period of pre operational stage is: 
Select and explain. 
A. Birth to 18 months, B. 12 years onwards., C. 2-6 years., D. 7-12 years.
C: 2-6 years.
Answer: C: 2-6 years. 
Explanation: According to Piaget Cognitive theory, the sequence of development has been categorized into 4 major stages:

Sensorimotor stage (0 to 2 yrs)
Pre-operational stage (2 to 6 yrs)
Concrete operation stage (7 to 12 yrs)
Formal operation stage (11 to 15 yrs)