Final answer:
Riley, who displayed exceptional drawing skills but struggled academically, can be characterized as a savant, indicating extraordinary capabilities in a specialized area but with challenges in other domains.
Step-by-step explanation:
Considering Riley's ability to draw a detailed and realistic-looking scene at the age of four but struggles with reading, math, science, and history, the term that would make the most sense to apply to Riley is savant. A savant is an individual who demonstrates profound and exceptional capacities or abilities far in excess of what would be considered normal, often including the ability to produce meticulous and detailed work in some specific field, much like the drawing skills displayed by Riley. However, savants may also experience challenges in other areas, as with Riley's difficulties in academic subjects.
Answer: C. savant