The chancellor of a major university was concerned about alcohol abuse on her campus and wanted to find out the proportion of students at her university who visited campus bars on the weekend before the final exam week. Her assistant took a random sample of 250 students. The total number of students in the sample who visited campus bars on the weekend before the final exam week is an example of (3.3分)3.3 分A、 a continuous random variable.B、a discrete random variable.C、a parameter. D、 a categorical random variable.