How does Denny's career as a race car driver relate to the broader themes of the story?

Denny's career as a race car driver serves as a powerful metaphor for the struggles and challenges faced in life, which is a central theme of "The Art of Racing in the Rain." Racing, like life, is unpredictable and fraught with obstacles. Denny's experiences on the racetrack mirror the personal challenges he encounters, such as dealing with financial hardships, family strife, and legal battles.

By navigating these difficulties on the racetrack, Denny exemplifies resilience and determination, demonstrating that success is not solely about winning but about how one responds to adversity. His journey illustrates the importance of perseverance and the ability to maintain focus even in the face of life's turbulence, reinforcing the novel's broader messages about love, loyalty, and the human spirit's capacity to endure.

The other options do not encompass the full scope of Denny's experiences. While the thrill of victory is a part of racing, it fails to capture the comprehensive struggles depicted in the story. Denny's career does not highlight irresponsibility or an obsession with fame, which are tangential to the deeper, more resonant themes of perseverance and the complexities of life.