Enteroliths are calcifications that form in the gut of a horse. The stones can cause considerable morbidity a mortality. A study was conducted to investigate factors such as diet and environment that may be related t the formation of enteroliths. The study contained seven stallions with their ages, in years, as follows: 10 20 4 13 21 The youngest stallion at 4 years old is: 16 OA. an outlier because it is the minimum. B. not an outlier because it is a positive value. 16 O C. not an outlier because it is less than 15 years below the lower quartile. D. an outlier because it is more than 15 years below the lower quartile.