Final answer:
The ten-year-old's story featuring a singing and dancing dog is best classified as fantasy, as it introduces magical elements into a realistic setting.
Step-by-step explanation:
Ten-year-old Richard wrote a story that begins realistically but includes a singing and dancing dog, thus the story could best be classified as a work of fantasy. Fantasy stories often start in a realistic setting but incorporate elements that are magical or supernatural, like animals performing human-like activities. It departs from creative nonfiction, which tells true stories using literary techniques and devices but stays within the realm of possibility.