In a Research Study of Anxiety in Adolescents, Anxiety Was

In a research study of anxiety in adolescents, anxiety was defined as a cut-off score on a questionnaire completed by each adolescent. This definition of anxiety

A) is unacceptable because anxiety must be defined by a measure of heart rate or sweating.
B) is referred to as the independent variable.
C) is referred to as an operational definition of the anxiety.
D) is unacceptable because adolescents are unable to provide accurate assessments of their feelings.