Which of the following is a breed of horse?

The correct answer, indicating that both Clydesdale and Thoroughbred are breeds of horses, reflects an understanding of the classification of horses. The Clydesdale is a large draft horse known for its strength and distinctive feathering on the lower legs, originally bred for heavy farm work and known for its gentle temperament. On the other hand, the Thoroughbred is a breed renowned for its speed and athleticism, primarily used in horse racing and other competitive equestrian disciplines.

While "Pony" refers to a category of horses that are smaller in stature rather than a specific breed, both Clydesdales and Thoroughbreds are recognized as distinct breeds with unique characteristics and histories. Therefore, recognizing that the question specifically asks for breeds solidifies the understanding that both Clydesdale and Thoroughbred meet that criterion, making the combination of both the correct and comprehensive choice.