Final answer:
The pylorus connects the stomach to the small intestine in horses, with the pyloric sphincter regulating the passage of chyme.
Step-by-step explanation:
The pylorus is a region of the stomach that connects the stomach to the small intestine. Its role involves controlling the passage of partially digested food, now referred to as chyme, from the stomach to the duodenum, the first part of the small intestine. The pylorus uses a muscular valve called the pyloric sphincter to release chyme gradually into the small intestine, which is crucial for further digestion and absorption. Therefore, in horses as well as in other mammals, the pylorus connects the stomach and the small intestine. Considering the provided choices for the digestive tract connection in horses, the correct answer is A. Stomach and Small intestine.