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 Piaget's Cognitive theory, the sequence of development has been categorized as: 
Select and explain. 
A. Sensorimotor stage, preoperational stage, concrete operational stage, formal operational stage., B. Sensorimotor stage, preoperational stage, formal operational stage, concrete operational stage., C. Pre-operational stage, sensorimotor stage, formal operational stage, concrete operational stage., D. Formal operational stage, preoperational stage, sensorimotor stage, concrete operational stage.
A: Sensorimotor stage, preoperational stage, concrete operational stage, formal operational stage.
Answer: A: Sensorimotor stage, preoperational stage, concrete operational stage, formal operational stage. 
Explanation: According to Piaget,  the ages between 6 and 12 roughly approximate the third  major developmental stage of cognition, that is, the phase of concrete operations. Piaget proposed  the following four major periods of intellectual development:

Sensorimotor: Birth to 18 months
Preoperational: 18 months to 7 years
Concrete operational: 7 to 12 years
Formal operational: 12 years and onward.

Pediatric Dentistry Infancy Through Adolescence Fourth Edition P: 469