Lily, a 4-year-old girl, is playing with blocks. She has never seen a triangle before and thinks it is a strange shape. She tries to fit the triangle block into the round hole of her shape-sorting toy, but it doesn't fit. She then tries to fit the triangle block into the triangle-shaped hole and finds that it fits perfectly. What term best describes the mental organizational framework that Lily has for understanding shapes?
Accommodation
Assimilation
Attachment
Schema