A group of veterinary researchers plans a study to estimate the average number of enteroliths in horses suffering from them. The number of enteroliths is determined by surgery or by ultrasound. This requires the participation of a surgeon and a radiologist in the study. To ensure correct counts, the researchers decide that they should only enroll horses seen at the best veterinary hospital in the country, which will typically see the most severe cases. The researchers will enroll the first 100 horses seen, beginning on the day the study is funded. The resulting interval is likely biased because: All of the answer options are correct. the first 100 horses seen is not an SRS of all horses with enteroliths and, therefore, never representative. the best veterinary hospital is likely to see the most severe cases, with larger numbers of enteroliths. a sample of 100 horses is too small to obtain an unbiased estimate.