Every year the veterinary hospital at a major research university treats a number of horses that have stones called enteroliths in their guts A sample of 20 years shows that on average about 2 of horses presenting a the veterinary hospital are treated for enteroliths Some breeds of horses seem more prone to developing enteroliths than others Below is a table with the distribution of enteroliths among the breeds Breed Arabian Thoroughbred Appaloosa 15 Quarter horse Probability 0 3 2 Morgan 10 The probability that a horse arriving at the veterinary hospital is not an Arabian or a quarter horse is O A 0 75 B 0 25 C 0 55 D 0 45