Which Statement Is an Operational Definition of a Concept

Which statement is an operational definition of a concept?

A) Death anxiety is an uncomfortable feeling on contemplation of one's own death, measured by Templar's Death Anxiety Scale (Templar, 1986) .
B) Pain is a pattern of responses to protect the organism from harm (Sternbach, 1979) .
C) Maternal identity entails maternal cognitions and affect with regard to the maternal-infant relational system (Walker and Montgomery, 1994) .
D) Spirituality is a way of being or experiencing that comes about through an awareness of a transcendent dimension and one's identifiable values with regard to self, other, nature, and whatever one considers to be ultimate (Elkins, 1988) .