In a database student enrollment status is coded in the following way: The code $"1"$ is used for full$-$time students, the code $"2"$ is used for part$-$time students in more than one course, the code $"3"$ is used for continuing education students and the code $"4"$ is used for dual$-$credit students. The variable being coded is an example of

a$)$ a Bernoulli Trial

b$)$ nominal data

c$)$ discrete quantitative data

d$)$ classes in histograms