A Questionnaire Contained the Item "Educational Level Completed" and Responses

Multiple Choice

A questionnaire contained the item "educational level completed" and responses of grade school, junior high school, high school, college, graduate degree, other. A researcher asked subjects to check the appropriate response. The researcher is using this question to measure​

A) ​direct observables.
B) ​indirect observables.
C) ​constructs.
D) ​a nominal variable.
E) ​validity.