Final answer:
The Schubert art song about a father and son riding through a spooky forest is 'Erlkönig'.
Step-by-step explanation:
The art song by Schubert that is about a man and his son riding through a spooky forest is a) Erlkönig. This song tells the dramatic and haunting story of a father racing to get his ill child to safety while the child is being terrorized by the mythical Erlkönig, who symbolizes death. It is one of Schubert's most famous Lieder (German art songs) and is known for its expressive and evocative music that captures the urgency of the father's ride and the fear of the son.