Cara belongs to a knitting group that meets at the local craft shop. From observations, she has hypothesized that people purchase knitting needles only if they are also purchasing yarn. To confirm her thinking, Cara surveyed five people who came into the shop at various times throughout the day and asked them about their past purchases. Which of these factors is the most likely to skew the results of Cara's observations? A. The participants are not randomized. B. The sample size is too small to represent the population. C. A control group is needed for an observational study. D. People have to buy yarn at a craft shop