Children in middle childhood are in Piaget's _______ stage, which extends from about 7 to 11 years.

The correct answer is C: concrete operational. During the concrete operational stage, children start to engage in logical thinking about concrete events. This stage typically occurs between the ages of 7 to 11 years. Choices A, B, and D are incorrect. The sensorimotor stage (choice A) is the first stage in Piaget's theory, occurring from birth to about 2 years old. The preoperational stage (choice B) follows the sensorimotor stage and occurs roughly from ages 2 to 7 years. The formal operational stage (choice D) is the final stage in Piaget's theory, where abstract thinking and hypothetical reasoning develop, usually beginning around age 11.