Answer: The stage of cognitive development that Reina is in is the The concrete operational stage.
Explanation: According to Jean Piaget's theory of development, there are four stages of development. They are; sensorimotor; preoperational; concrete; and formal operational stages.
The concrete operational stage occurs in children between the age of 7 to 11 and in this stage, the child has learned to think in a logical manner if they are familiar with the concepts. Reina earning A's on her math tests is because she's already familiar with the concepts of multiplication and division.