B is correct. “The median is the value of the middle item of a set of items. In an even-numbered sample, we define the median as the mean of the values of items occupying the n/2 and (n +2)/2 positions” (p. 362). The n/2 item is the 10th item, and the (n +2)/2 item is the 11th item. The value of the 10th item is 3; the value of the 11th item is 5. The mean of 3 and 5 is 4.