Final answer:
Piaget's four stages of development are the sensorimotor, preoperational, concrete operational, and formal operational stages. Object permanence is a milestone in the sensorimotor stage where children understand that objects still exist even when out of sight.
Step-by-step explanation:
Piaget's four stages of development are the sensorimotor, preoperational, concrete operational, and formal operational stages. In the sensorimotor stage, which lasts from birth to about 2 years old, children develop object permanence, the understanding that objects still exist even when they are out of sight. In the preoperational stage, which is from approximately 2 to 7 years old, children use symbols to represent words and ideas but have not developed logical manipulation of information. The concrete operational stage, which occurs from about 7 to 11 years old, is characterized by logical thinking about real events and the understanding of conservation. The formal operational stage, from about age 11 to adulthood, involves the ability to think abstractly and solve problems using abstract thinking. Therefore, option A is supported by Piaget's theory.