Sue taylor, director of global industrial sales, is concerned by a deteriorating sales trend. specifically, the number of customers is stable at 1,500, but they are purchasing less each year. she orders her staff to search for causes of the downward trend by surveying all 1,500 industrial customers. one question on the survey asked the customers: "which of the following best describes your primary business:
a. manufacturing,
b. wholesaler,
c. retail,
d. service."
the measurement level for this question is