D. The selection and placement of materialsThe other options are less relevant:a. Sorting and classifying refers to a specific cognitive skill, not the selection of materials.b. The "smart" classroom refers to classrooms equipped with advanced technology, but doesn't specifically address the selection of age-appropriate materials.c. Issuing a credit card is unrelated to the context of early childhood education.e. Pre-determined Dreaming seems irrelevant to the topic as it doesn't connect to the process of selecting educational materials.