Final answer:
Piaget proposed four stages of cognitive development: sensorimotor, preoperational, concrete operational, and formal operational. So, the correct answer is option a.
Step-by-step explanation:
Piaget proposed a theory of cognitive development that consists of four stages: sensorimotor, preoperational, concrete operational, and formal operational. The sensorimotor stage occurs from birth to around 2 years old, during which children learn about the world through their senses and motor behavior. The preoperational stage is from approximately 2 to 7 years old, where children can use symbols and engage in pretend play but cannot understand adult logic.
The concrete operational stage takes place from about 7 to 11 years old, during which children can think logically about real events and understand concepts like conservation. Finally, the formal operational stage begins around age 11 and continues into adulthood, where individuals can think abstractly and solve problems using hypothetical situations.
So, the correct answer is option a.