Answer: D. Focuses on the development of logic
Explanation: According to Piaget's theory of cognitive development, this phase is the third in a row. It lasts roughly, from the seventh to the eleventh year, that is, the period of the so-called middle childhood, and at this stage logical thinking develops. In this period, children develop concrete mental activities related to specific, concrete situations. For example, if no one took part of something, then it was left in the same amount as before. Such concrete mental activities that are associated with a particular object begin to be an essential part of knowledge. In other words, rational thinking develops.